Sinapoyl malate, naturally present in plants, has proved to be an exceptional UV filter and molecular heater for plants. Although there are nowadays industrially relevant sustainable synthetic routes to sinapoyl malate, its incorporation into certain cosmetic formulations, as well as its adsorption on plant leaves, is limited by its hydrophilicity. To overcome these obstacles, it is important to find a way to effectively control the hydrophilic–lipophilic balance of sinapoyl malate to make it readily compatible with the cosmetic formulations and stick on the waxy cuticle of leaves. To this end, herein, we describe a highly regioselective chemo-enzymatic synthesis of sinapoyl malate analogues possessing fatty aliphatic chains of variable length, enabling the lipophilicity of the compounds to be modulated. The potential toxicity (i.e., mutagenicity, carcinogenicity, endocrine disruption, acute and repeated-dose toxicity), bioaccumulation, persistence and biodegradability potential of these new analogues were evaluated in silico, along with the study of their transient absorption spectroscopy, their photostability as well as their photodegradation products.
The use of several ingredients in cosmetic formulations can often result in long ingredient lists, which can be daunting for consumers. While each of these particular ingredients serves a purpose, some are petroleum-based and may have adverse effects on the environment and human health. Ferulic acid, a p-hydroxycinnamic acid present in numerous agro-industrial byproducts, exhibits antimicrobial, antioxidant, and UV-filtering properties. In this work, ferulic acid was functionalized through chemoenzymatic reaction steps (80 to 93% isolated yields) applying green chemistry principles, by using various natural fatty alcohols. The resulting compounds have demonstrated good emollient properties through physicochemical and spreading evaluations. Two green metrics (Mass Intensity and Ecoscale) were used to assess the synthesis of these novel emollients, which were found to have a very low environmental impact. The findings of this study could provide a novel solution for multifunctional, biobased ingredients in cosmetic formulations while reducing the environmental impact of the products.
This opinion paper explores the potential of integrating synthetic biology into microbial polymers to produce tailored biopolymers for food packaging applications. Synthetic biology has shown precise control over metabolic machinery, enabling the manipulation of pathways involved in microbial biopolymer production. However, there is limited literature available on utilizing the same pathways for designing tailored biopolymers suitable as efficient food contact materials. This is primarily due to the regulatory status of microbial polymers as determined by food safety authorities. One possible solution is to leverage synthetic biology tools by adopting safety assessment protocols established within the regulatory framework. By considering the advantages of synthetic biology-driven microbial polymers, this innovative approach has the potential, not only to replace conventional methods but also to provide additional value by addressing environmental concerns associated with traditional food packaging.
The present research article delves into the preparation of a new class of bio-based polyesters from α,ω-diene furandicarboxylate monomers. In particular, it exploits the use of acyclic diene metathesis polymerisation (ADMET) on 2,5-furandicarboxylic acid (FDCA)-derived compounds. First, a library of furan-based α,ω-diene monomers was prepared via acid- or base-catalyzed transesterification of 2,5-furandicarboxylic acid dimethyl ester (FDME) with commercially available alcohols incorporating terminal olefins, i. e., allyl alcohol, but-3-en-1-ol, hex-5-en-1-ol and dec-9-en-1-ol. Then, the novel monomers were subjected to ADMET polymerisation employing different catalysts and reaction conditions. Interestingly, first-generation Grubbs catalyst was found to be the best promoter for ADMET polymerisation. This catalyst allowed the preparation of a new family of bio-based polyesters with molecular weights up to 26.4 kDa, with good thermal stability, and adaptable cis-trans conformations. Results also revealed that the monomer structure had a direct impact on the polymerisation efficiency and the resulting thermal properties. The effect of green bio-based solvents such as Cyrene™, dimethyl isosorbide (DMI) and γ-valerolactone (GVL) on the polymerisation process was also studied. Data collected showed that the solvent concentration influenced both the yield and length of polymers formed. Furthermore, some co-polymerisation experiments were conducted; the successful integration of different monomers in the resulting copolymer was shown to affect the glass transition temperature (Tg) of the resulting materials.
This study focuses on the recovery of sinapic acid using liquid–liquid extraction (LLE) assisted by a hollow fiber membrane contactor (HFMC) from an aqueous feed obtained through the hydrolysis of mustard bran. The hydrolyste contains 230 ± 36 mg/L of sinapic acid, with a natural pH of 4. A screening was performed with solvents of different chemical nature (alcohol, ester, ketone, ether, cyclic ether). Data showed that all the solvents tested gave an extraction efficiency of more than 80 % for pH < 5, whereas the initial concentration of sinapic acid in the aqueous feed has little impact on the extraction efficiency. Four of the solvents tested were selected for use in the HFMC: two volatile (CPME, MIBK) and two non-volatile (octanol, octyl acetate). The solubility of the volatile solvents in the feed phase was found to be an important factor to consider in evaluating the HFMC (2.6 ± 0.5 % and 1.07 ± 0.05 % v/v with MIBK and CPME, respectively). Mass transfer coefficients with volatile solvents (25 ± 1 x10-6 and 15.3 ± 0.5 x10-6 m/s for MIBK and CPME, respectively) exceeded those of non-volatile solvents (4.1 ± 0.2 x10-6 and 4.5 ± 0.5 x10-6 for octanol and octyl acetate, respectively) by 4- to 6-fold. Extraction was intensified by increasing the initial concentration of sinapic acid in the feed phase and by increasing the feed-to-solvent ratio. CPME demonstrated optimal recovery efficiency at a phase ratio of 8:1 (v/v), yielding 0.9 g of sinapic acid per liter of CPME used.
A novel method for synthesizing biobased diamide tetraol derivatives through mechanochemical processes is presented in this study. The key component used in the synthesis is (S)-γ-hydroxymethyl-γ-butyrolactone (2H-HBO), a cellulose-based lactone derived from levoglucosenone, combined with various linear diamines. The use of planetary ball milling in the presence of a small excess of diamine was found to be crucial for achieving complete conversion of 2H-HBO and the selective formation of diamide tetraol derivatives. The optimized parameters established for the reaction of 2H-HBO using diaminohexane were applied to biobased, non-toxic, and biodegradable diamines such as spermidine, spermine, and 4,9-dioxa-dodecanediamine. This resulted in high conversions and good yields of diamide tetraol derivatives. The scalability of the process was demonstrated by transposing the reaction from 100 mg to 2 g, with improved conversions obtained at a larger scale. The greenness of the procedure was assessed using the E-factor and EcoScale, showing low waste generation and acceptable to excellent reaction conditions. In addition, enzymatic polymerization of diamide tetraol derivatives using CAL-B (Candida antarctica lipase B) as a biocatalyst was explored. Successful polymerization of monomers obtained from hexamethylene diamine and 4,9-dioxa-dodecandiamine was achieved, providing insights into the effect of enzyme loading and monomer ratios on the molecular weight of the resulting polymers. Despite challenges with certain monomers containing amine groups, this work offers a promising approach for producing multifunctional biobased polymers.
A new class of furanic α,ω-dienes was synthesized by using cellulose-derived 2,5-bis(hydroxymethyl)furan as a renewable starting material. The ability of these monomers to undergo acyclic diene metathesis polymerization was investigated under various reaction conditions, including type of metathesis catalyst and catalyst loading. The resulting biobased polyethers were characterized through high-performance size exclusion chromatography, differential scanning calorimetry, and thermal gravimetric analysis. The novel polymers showed molecular weights up to 43 kDa and exhibited good thermal stability (Td5% up to 301 °C) and low glass-transition temperatures (−67 °C < Tg < −24 °C). Polymerization reactions were also conducted employing selected green solvents (Cyrene, dimethyl isosorbide, and γ-valerolactone), and the results were compared to those of the solvent-free procedure. Finally, in order to increase the Tg values of the polyethers, copolymerization experiments were performed employing the best performing furanic α,ω-diene as well as a biobased aromatic monomer derived from syringaresinol.
This study focuses on the synthesis of fully renewable polycarbonates (PCs) starting from cellulose-based platform molecules levoglucosenone (LGO) and 2,5-bis(hydroxymethyl)furan (BHMF). These unique bio-based PCs were obtained through the reaction of a citronellol-containing triol (Triol-citro) derived from LGO, with a dimethyl carbonate derivative of BHMF (BHMF-DC). Solvent-free polymerizations were targeted to minimize waste generation and promote an eco-friendly approach with a favorable environmental factor (E-factor). The choice of metal catalyst during polymerization significantly influenced the polymer properties, resulting in high molecular weight (up to 755 kDa) when Na2CO3 was employed as inexpensive catalyst. Characterization using Nuclear Magnetic Resonance (NMR) confirmed the successful incorporation of the furan ring and the retention of the terminal double bond of citronellol pendant chain. Furthermore, under ultraviolet (UV) irradiation, the presence of both citronellol and furanic moieties induced singular structural changes, triggering the formation of three distinct structures within the polymer network, a phenomenon herein observed for the first time in this type of polymers. These findings pave the way to new functional materials prepared from renewable monomers with tunable properties.
Sustainability assessment of polymer production processes is of utmost importance to evaluate their environmental, social and economic impact, but it remains poorly studied. This chapter aims to raise the awareness of researchers and readers in academia, industry and civil society about this issue and some of the easy and straightforward methods to assess the greenness of polymers. To that end, it begins with an overview of polymer waste reduction, followed by the main methods of reducing the waste generated. It then describes in more details how readily available green metrics, such as environmental factor (E-factor), can help to assess manufacturing processes and polymer products, and identify areas where improvements can be made. Then, it describes methods that can be used in conjunction with E-factor to better assess the sustainability of a production process, while also showing the limitations/challenges linked to these methods. The main approaches to polymer development from biomass are presented, followed by a focus on E-factor calculations of examples of the widely used lignin-derived monomers and polymers (e.g., vanillin), as well as the rapidly evolving field of levoglucosenone-derived monomers and polymers. Future directions for improving the field of (sustainable) polymer chemistry is also provided.
3D-printing technologies for polymeric formulations are experiencing a huge development due to the complex and specific geometries that can be covered employing additive manufacturing. However, to ensure sustainable growth, it is essential to replace the currently used fossil-based resins with new bio-sourced alternatives. In this study, tunable bis-allylated compounds were efficiently synthesized from cellulose-derived levoglucosenone via a chemo-enzymatic pathway whom greenness has been assessed by E-factor and Eco-Scale. Subsequently, photocuring was employed as an eco-friendly process to polymerize these compounds with a trifunctional thiol using thiol-ene click chemistry. Real-time techniques such as FT-IR, photo-DSC, and photo-rheology were employed to extensively characterize the UV-process. The resulting thermosets were also subjected to a thorough analysis, covering their thermal-mechanical properties and degradation. Owing to the exceptional reactivity of this thiol-ene system, 3-D printed materials were achieved with remarkable precision.
One trend in agriculture is the replacement of classical pesticides with more ecofriendly solutions, such as elicitation, which is a promising approach consisting of stimulating the natural immune system of a plant to improve its resistance to pathogens. In this fashion, a library of p-coumaric-based compounds were synthesized in accordance with as many principles of green chemistry as possible. Then, these molecules were tested for (1) the direct inhibition of mycelium growth of two pathogens, Botrytis cinerea and Sclerotinia sclerotiorum, and (2) plasma membrane destabilization in Arabidopsis and rapeseed. Finally, the protective effect was evaluated on an Arabidopsis/B. cinerea pathosystem. Total inhibition of the growth of both fungi could be achieved, and significant ion leakage was observed using dihydroxylated fatty p-coumarate esters. A direct effect on plants was also recorded as a ca. three-fold reduction in the necrosis area.
Resveratrol dimers are of great interest for pharmaceutical and cosmetic applications. Nevertheless, the yield of their bioproduction is limited by both the competition between the possible radical–radical coupling pathways and complex isolation procedures. Alternative organic synthesis methods do not afford higher yields. Although enzymatic routes can provide dimers in one step from resveratrol, biocatalysis optimization is required to improve yields and orient radical–radical coupling selectivity toward a specific resveratrol dimer, E-labruscol herein.
After a rapid study of the relative importance of the biocatalysis parameters, a design of experiments was implemented to produce E-labruscol in high yield by laccase-mediated dimerization of resveratrol. E-labruscol and δ-viniferin were identified and isolated by flash chromatography as major products in 21 and 52% yields, respectively. As an alternative to purification on silica gel, efficient separation of the aforementioned compounds was achieved by centrifugal partition chromatography (CPC).
This technology provided δ-viniferin in 63.1% yield (90% purity) and labruscol isomers in 20.4% yield with a purity of 95% after a CPC polishing step, but it also revealed the presence of E-labruscol diastereomers, leachianol F and leachianol G, as major reaction products, as well as less abundant products: pallidol, Z-labruscol, ε-viniferin, and two new resveratrol dimers named iso-δ-viniferin and iso-ε-viniferin.
Brewers' grains (BSG), the main waste product of the beer industry, are widely available and rich in fiber and bioactive compounds. Ferulic acid (FA) is the main phenolic compound in BSG, it has antioxidant and antibacterial properties that make it a valuable product for cosmetic, food and pharmaceutical industries. Alkaline hydrolysis is the common technology for extracting FA from biomass, this technology needs to be substituted as it is non-selective and requires harsh conditions making purification more complicated and expensive. This research work presents enzymatic hydrolysis as a green alternative for FA extraction. Five commercial enzymes were screened and compared for their hydrolytic efficiency to release FA. Prior to the enzymatic hydrolysis, autoclave was selected as the most effective pretreatment. Depol 740L was selected as the desired enzyme based on its high feruloyl esterase activity (0.4 U/mL). The enzymatic extraction parameters (pH, temperature and enzyme dosage) were optimized using response surface methodology. The highest FA recovery, 1.06 ± 0.01 mg/g dry weight (43.13% in comparison with the alkaline hydrolysis), could be achieved at pH 5.27; temperature 60 °C and 1.72% enzyme. The optimal extraction conditions were found to be sufficient within 22 h, as determined by a kinetic study.
This study aimed to investigate the effect of an innovative ecofriendly process—instant controlled pressure drop technology, also known as “détente instantanée contrôlée” or DIC—coupled with Tripolium extraction (DIC-Tripolium), on the hesperidin recovery, and antioxidant and antidiabetic activities of orange byproduct extracts. A DIC pretreatment was applied to partially dried orange byproducts (~16% wet basis). A central composite rotatable design (CCRD), composed of 13 experimental trials (four factorial points, four-star points, and five repetitions for the central point), was followed by a Tripolium process consisting of successive intermittent extraction periods using ethanol/water solvent at 20 ± 1 °C, 5 kPa for 5 min and m/v ratio = 5 g/50 mL. The DIC pretreatment, coupled with the Tripolium process, increased the extractability of hesperidin (from 1.55- to 4.67-fold compared to untreated DIC orange byproducts). The radical scavenging activities of the extracts were also enhanced or preserved in different DIC–Tripolium extracts. The α-Amylase inhibition percentage varied between 55.6 ± 0.02 and 88.30 ± 0.01% according to DIC–Tripolium conditions. The multi-criteria optimized condition of DIC–Tripolium extraction, allowing for the maximization of the hesperidin content, radical scavenging activities, iron chelating activity, and α-amylase inhibition of extracts, corresponds to a DIC saturated steam pressure of 599.4 kPa and a DIC pretreatment time of 38 s.
The use of membrane contactors (MC) for the recovery of biomolecules in biorefinery processes has become increasingly popular thanks to their desirable properties such as robustness, large surface area, modularity and flexibility, as well as their non-dispersive nature. This review article provides a recent comprehensive and critical look into the recent progress made in the application of MC for the recovery of biomolecules such as aroma compounds (acetophenone, 2-phenylethanol, etc.), butanol, antibiotics, and organic acids from aqueous media and fermentation broths. Although some previous reviews have discussed the design and operation of membrane contactors for applications such as dissolved gases management and CO2 capture, this review focuses on the liquid-liquid extraction of biomolecules from biorefinery liquid streams. It includes a detailed discussion of the technical characteristics of MC and their applications for liquid-liquid extraction of organic molecules from bioconversion and liquid media. A focus is then put on the use of MC for the extraction of organic acids, looking at the effects of operating conditions, extracting phase, and feed phase on the extraction process, as well as proposing back-extraction of organic acids by MC. Some of the challenges and limitations currently associated with these applications are highlighted.
The microfluidic production of simple (microspheres) and core–shell (microcapsules) polymer microparticles, often called microencapsulation, has been the scope of several research works since the 1980s. It is a fast, thrifty, and efficient process because of its controlled properties, tuneability, and yield, which can reach 100%. However, the question of its greenness, sustainability, and scalability remains unclear, and more awareness/education is required in this field. The sustainability of production processes using microfluidic techniques can be realized/discussed based on three pillars: (i) waste generation, (ii) the solvents employed, and (iii) raw materials. On the other hand, although the scaling-up of these processes was reported on in several papers as procedures in which hundreds or thousands of microfluidic chips are set in parallel, the sustainability of this scale-up has not been addressed to our knowledge. This opinion paper highlights the advantages of microfluidic encapsulation processes, their greenness according to the above-mentioned pillars, (i–iii) and the necessary considerations to scale them up while preserving their sustainability.
With an increasing demand for safe and natural products from both industries and consumers, paired with the recent ban of decried molecules (i.e. octinoxate, avobenzone or octocrylene) due to their high negative impact on humans and the environment (i.e. endocrine disruption, coral bleaching), safe bio-based alternatives are a necessary and promising surrogate to substitute current commercialized petroleum-based UV filters. In this context, a class of bio-based molecules, displaying interesting UV-B filtering properties and great photostability were developed from furfural and 5-hydroxymethylfurfural (HMF), using the Knoevenagel condensation with a set of green conditions to minimize the impact on environment. Furthermore, those furfural- and HMF-based molecules demonstrated antimicrobial properties as secondary activity, highly sought by industries. Some furan derivatives being recognized to exhibit toxicological risks, in silico and in vitro assays were conducted and demonstrated the absence of endocrine disruption activity for these new molecules.
In this study, using a model solution corresponding to the final medium composition of the NADP+ enzymatic production, we present for the first time a sustainable and simple alternative membrane-based filtration process that readily provides NADP+ in high purity. A membrane selection was first performed, and the GE membrane (Suez Water Technologies & Solutions (USA)) was shown to provide the best NADP+ retention rate >80% at 4 bar. An enzymatic strategy based on the addition of a commercial ATP diphosphohydrolase (apyrase from potatoes) to the model solution significantly simplified the composition of the medium, resulting in a very good discrimination profile between NADP+ and AMP retention (69.3% gap) on the one side, and NADP+ and adenine (87.5% gap) on the other. These data allowed to predict a profile of purity and loss of NADP+ as a function of diafiltration volume (DV). According to these predictions, a >90% purity could be achieved after only 4 DV, demonstrating that this membrane-based purification method achieves a very high purity rate of NADP+ while being competitive compared to the other conventional methods currently used.
The orange byproduct is a widely accessible and valuable source of functional phenolic compounds, particularly hesperidin. Hesperidin extraction remains a challenging phase in its valorization chain due to its low solubility and limited extractability in solvents. This work aims to examine the effect of conventional solvent extraction (CSE) compared to emerging and innovative extraction methods: accelerated solvent extraction (ASE) and ultrasound-assisted extraction (UAE) when applied with or without a pretreatment process of instant controlled pressure drop (DIC) to intensify extraction, antioxidant, and antidiabetic activities. The total phenols, flavonoids, hesperidin contents, radical scavenging activities, iron chelating activity, and in vitro α-amylase inhibition of the extracts were determined for CSE (80%, 70 °C), UAE (ethanol 80%, 70 °C, 200 W), and ASE (ethanol 60%, 100 °C, 100 bars) with or without DIC pretreatment (pressure = 0.4 MPa, total thermal time = 30 s). The hesperidin amounts obtained were 0.771 ± 0.008 g/100 g DM, 0.823 ± 0.054 g/100 g DM, and 1.368 ± 0.058 g/100 g DM, for CSE, UAE, and ASE, respectively. DIC pretreatment of orange byproducts increased hesperidin recovery by 67%, 25.6%, and 141% for DIC-CSE, DIC-UAE, and DIC-ASE, respectively. The DPPH and ABTS radical scavenging and iron chelating activities of extracts were also significantly enhanced, and the in vitro antidiabetic activity of extracts was preserved.
Easily detachable and reusable adhesives are attractive as single-use adhesive replacements to reduce waste and promote reuse, recycling, or even upcycling options. Lignin, the second most abundant polymer and a byproduct of the paper-pulp industry, was utilized to design a novel, highly tunable reversible polymer adhesive. The approach adopted was to take advantage of the photo-responsive property of the α,β-unsaturated ester moiety of the p-hydroxycinnamic acid structure synthesized in this work using lignin-oxidation compounds and modified to attain reversible adhesion switching. The reversibility is achieved by the exposure of UV light that cleaves the covalent cyclobutane rings originally formed from the α,β-unsaturated bond of the ester, which softens the material and makes it easily separable. The original polymer structure can be established again by recrosslinking to offer reworkability. The design of experiments (DoE) method was introduced to optimize the significant variables to achieve optimum lap shear strength for the adhesive. The effect of various structural aspects shows a high tunability of the structure to meet the property requirements. The design strategy of the polymer adhesive from renewable resources, along with the structure–property analysis mechanisms described in this work, can be implemented to engineer new bio-based and reusable adhesives.
Sinapine is a phenolic compound found in mustard (Brassica juncea) seed meal. It has numerous beneficial properties such as antitumor, neuroprotective, antioxidant, and hepatoprotective effects, making its extraction relevant. In this study, the extraction of sinapine was investigated using three methods: (i) from a mustard seed meal defatted by a supercritical CO2 (SC-CO2) pretreatment, (ii) by the implementation of high-voltage electrical discharges (HVEDs), (iii) and by the use of ultrasound. The use of SC-CO2 pretreatment resulted in a dual effect on the valorization of mustard seed meal, acting as a green solvent for oil recovery and increasing the yield of extracted sinapine by 24.4% compared to the control. The combination of ultrasound and SC-CO2 pretreatment further increased the yield of sinapine by 32%. The optimal conditions for ultrasound-assisted extraction, determined through a response surface methodology, are a temperature of 75 °C, 70% ethanol, and 100% ultrasound amplitude, resulting in a sinapine yield of 6.90 ± 0.03 mg/g dry matter. In contrast, the application of HVEDs in the extraction process was not optimized, as it led to the degradation of sinapine even at low-energy inputs.
The use of sustainable raw materials is now a necessity in all industries, including the production of porous microparticles. Cyrene™ is a cellulose-derived compound that is readily prepared through the reduction of the α,β-unsaturation of levoglucosenone (LGO)—a wood-based platform molecule. In this work, the importance of Cyrene™ as a potential bio-based molecule to produce sustainable porous microparticles is demonstrated. First, a methacrylic derivative of Cyrene™ (m-Cyrene) was synthesized. A microfluidic co-flow device was then established to produce m-Cyrene-based oil-in-water (O/W) controlled-size emulsions and to polymerize them by ultraviolet (UV) radiation in a vial. The continuous phase was a sodium dodecyl sulfate aqueous solution, and the dispersed phase was a mixture of m-Cyrene with methacrylic anhydride (MAN) at two different mass concentrations (i.e., 1 wt.% MAN and 92 wt.% MAN) and 2,2-dimethoxy-2-phenylacetophenone (DMPA) as a photoinitiator. The process used the lowest possible quantity of raw materials and avoided excessive purifications to produce homogeneous porous m-Cyrene-MAN microparticles. The controlled size and homogeneous size distribution of the produced polymer microparticles were confirmed by scanning electron microscope (SEM) images. The 3D microstructure as well as the porosity were determined using X-ray microtomography. The high-resolution 3D images produced indicate that the pores of the microparticles are homogeneous and that their porosity is controllable through the concentration of MAN in the monomer mixture (porosity of 30% for a 1 wt.% MAN ratio and 2% for a 92 wt.% MAN ratio). Such porosity control is very important for future potential encapsulation processes that require precise release control. Keywords: sustainable production; size control; Cyrene™; microtomography; porosity
A new class of biobased composites with tailorable mechanical properties made of natural fibers, polylactic acid, and ferulic acid derivatives (FAD) is studied. FAD was used to develop composites with elastomeric properties like improved elongation at break and highly reversible deformation upon elongation. Composites were prepared using raw and enzymatically treated hemp fibers. The fibers were defibrillated due to the enzymatic treatment increasing their aspect ratio. The composites were characterized by their mechanical properties and their reaction to fire. No significant change in the dispersion of the fibers in the composites was reported. Homogenously dispersed crystallites of FAD were observed by scanning electron microscopy in the PLA matrix and at the interface between the PLA and the fibers, where they are suspected to increase the free volume in correlation with a decrease in mechanical properties following the increase in the aspect ratio of the fibers. FAD also degraded the reaction to fire of the material with an increase in 10% of the peak of Heat Release Rate (pHRR) in comparison to neat PLA. It also increased the charring residue up to 3 wt.%. A synergistic effect between FAD and the lignin increasing the charring residue is also reported.
Ferulic acid displays poor thermal resistance during extrusion and compression moulding, slow 2,2-diphenyl-1-picrylhydrazyl (DPPH) reaction kinetics, and undetected release from polylactide (PLA) and polyhydroxyalkanoates (PHA)-based films into polar mediums. Thus, in this study, a ferulic acid derivative Bis-O-dihydroferuloyl-1,4-butanediol (BDF) was used as an active additive (up to 40 w%) in PLA, poly(3-hydroxybutyrate) (PHB), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) matrices to produce blends by extrusion.
These blends were then used to prepare films by solvent casting. The BDF displayed good stability with 86-93% retention. The release kinetics in Food Simulant A revealed higher BDF release amounts (1.16-3.2%) for PHA-based films as compared to PLA. The BDF displayed faster DPPH reaction kinetics as compared to ferulic acid. The PHA-based films containing BDF displayed > 80% of DPPH inhibition. The growth of crystals inside polymer matrix had a nucleation effect which reduced the glass transition temperature of the films.
Polyesters are important materials with a wide range of applications, but there has been increasing concern over their sustainability. One example is the need for safer, bio-derived solvents to replace those currently in use for the polymer’s synthesis and processing. In this work, several variants of the bio-based cellulose/levoglucosenone derived solvent Cyrene, namely the ketal derivatives dioxolane Cygnet, dioxane Cygnet and dioxepane Cygnet were synthesized and tested as media for enzymatic polycondensation reactions using bio-based building blocks. Dioxolane Cygnet and dioxepane Cygnet were found to be suitable solvents for enzymatic polycondensation reactions, with dioxolane Cygnet being the preferred solvent, yielding polymers with a Mn >22 kDa. In addition, these solvents were tested in the biocatalyzed synthesis of levoglucosenone-based polyesters. The alternative solvents gave superior yields to those previously observed, demonstrating the versatility of these solvents in enzymatic polycondensation reactions, representing the first synthetic polymer-solvent system fully derived from cellulose.
This study focuses on the extraction of bioactive compounds from clary sage (Salvia sclarea L.) distillation residue with carbon dioxide under supercritical conditions. The target component is rosmarinic acid, a naturally occurring phenolic compound with strong antioxidant properties. Response surface methodology was applied to optimize the operating temperature, pressure and the co-solvent composition in the range of 40–100 °C, 100–600 bar, and 0–100 % ethanol in water (v/v), respectively.
The quantification of rosmarinic acid was performed using HPLC and the antioxidant activity of extracts was measured using DPPH assay. Results showed that the yield of extraction of rosmarinic acid and the antioxidant activity of the extracts varied significantly at each extraction condition. Based on the optimization study, the optimum pressure, temperature and the composition of the co-solvent were 100 bar, 65 °C and 35 % ethanol, respectively, with more than 8 mg/g of rosmarinic acid concentration obtained.
Levoglucosenone (LGO) - which possesses two chiral centers, a ketal and one α,β-unsaturated ketone moieties - is a high value renewable chiral building block that can be used for the production of a wide range of bio-based fine chemicals and polymers, as well as green solvents. This mini-review illustrates the different main strategies that have been developed to produce LGO from different starting materials such as lignocellulosic biomass, pure cellulose, sugars and non-sugar compounds.
Green synthesis of renewable alternatives to fossil fuel-based (macro)molecules/polymers is more than ever a necessity. We recently developed a sustainable pathway to produce 6-hydroxy-5,7-dimethoxy-2-naphthoic acid (DMNA), which resembles the fossil-derived 6-hydroxy-2-naphthoic acid, from sinapic acid. To investigate the potential of DMNA as a building block for polymer syntheses, three novel DMNA-derived α,ω-dienes (M1–M3) were synthesized and engaged in acyclic-diene metathesis (ADMET) polymerization in a three-step study to prepare renewable aliphatic-aromatic polyesters (P1–P3). Furthermore, the results showed that the properties can be finely tuned depending on the monomer and catalyst loading. Thermal analysis demonstrated that the glass transition temperature (Tg) and the temperature at which 5% of the mass is lost (Td5%) varied depending on the alkene chain length. A general thermal trend was established: Tg(P1) > Tg(P2) > Tg(P3) and Td5%(P1) < Td5%(P2) < Td5%(P3).
The first step aimed to evaluate the activity of seven commercial metathesis catalysts for the solvent-free ADMET polymerization of M3. Although most of the studied catalysts exhibited good reactivity, the second-generation Hoveyda–Grubbs catalyst (C4) proved the best.
The second step was then started by varying the catalyst loading and testing M1 and M2 toward ADMET polymerization. Aliphatic-aromatic polyesters with a number-average molecular weight (Mn) up to 19.4 kDa (Đ = 1.88) were obtained. Furthermore, the results showed that the properties can be finely tuned depending on the monomer and catalyst loading. Thermal analysis demonstrated that the glass transition temperature (Tg) and the temperature at which 5% of the mass is lost (Td5%) varied depending on the alkene chain length. A general thermal trend was established: Tg(P1) > Tg(P2) > Tg(P3) and Td5%(P1) < Td5%(P2) < Td5%(P3).
The third step of the ADMET study was to evaluate the tolerance of M1–M3 and C4 toward Cyrene, a green and high boiling point solvent derived from cellulose. The results revealed that Cyrene merits further investigation as a “general” non-toxic solvent for ADMET polymerization of other monomers, particularly those with high melting points.
Hydrogen and carbon dioxide fermentation to methane, called bio-methanation, is a promising way to provide renewable and easy-to-store energy. The main challenge of bio-methanation is the low gas-to-liquid transfer of hydrogen. Gas injection through a porous membrane can be used to obtain microbubbles and high gas-to-liquid transfer. However, the understanding of bubble formation using a membrane in the fermentation broth is still missing. This study focused on the impact of liquid pressure and flow rate in the membrane, gas flow rate, membrane hydrophobicity, surface, and pore size on the overall gas-to-liquid mass transfer coefficient (KLa) for hydrogen with gas injection through a porous membrane in real fermentation conditions. It has been shown that KLa increased by 13% with an increase in liquid pressure from 0.5 bar to 1.5 bar. The use of a hydrophilic membrane increased the KLa by 17% compared to the hydrophobic membrane. The membrane with a pore size of 0.1 µm produced a higher KLa value compared to 50 and 300 kDa. The liquid crossflow velocity did not impact the KLa in the studied range.
Solar exposure of avobenzone, one of the most widely used commercial UVA filters on the market, is known to cause significant degradation. This finding has fueled research into developing photostabilizer molecules. In an effort to provide insight into their stand-alone photoprotection properties, the excited state dynamics of the photostabilizer, 3-(3,4,5-trimethoxybenzylidene) pentane-2,4-dione (TMBP), and its phenolic derivative, 3-(4-hydroxy-3,5-dimethoxybenzylidene) pentane-2,4-dione (DMBP), were studied with ultrafast transient absorption spectroscopy. Solutions of TMPB and DMBP in ethanol and in an industry-standard emollient, as well as TMBP and DMBP deposited on synthetic skin mimic, were investigated. These experiments were allied with computational methods to aid interpretation of the experimental data. Upon photoexcitation, these photostabilizers repopulate the electronic ground state via nonradiative decay within a few picoseconds involving a twisted intramolecular charge transfer configuration in the excited state, followed by internal conversion and subsequent vibrational cooling in the ground state. This finding implies that, aside from acting as a photostabilizer to certain UV filters, TMBP and DMBP may offer additional photoprotection in a sunscreen formulation as a stand-alone UV filter. Finally, TMBP and DMBP could also find applications as molecular photon-to-heat converters.
Sinapate esters have been extensively studied for their potential application in ‘nature-inspired’ photoprotection. There is general consensus that the relaxation mechanism of sinapate esters following photoexcitation with ultraviolet radiation is mediated by geometric isomerization. This has been largely inferred through indirect studies involving transient electronic absorption spectroscopy in conjunction with steady-state spectroscopies. However, to-date, there is no direct experimental evidence tracking the formation of the photoisomer in real-time. Using transient vibrational absorption spectroscopy, we report on the direct structural changes that occur upon photoexcitation, resulting in the photoisomer formation. Our mechanistic analysis predicts that, from the photoprepared ππ* state, internal conversion takes place through a conical intersection (CI) near the geometry of the initial isomer. Our calculations suggest that different CI topographies at relevant points on the seam of intersection may influence the isomerization yield. Altogether, we provide compelling evidence suggesting that a sinapate ester’s geometric isomerization can be a more complex dynamical process than originally thought.
In this study, the definition and optimization of a medium for cost-effective heterologous production as well as efficient recovery of the plant secondary metabolite p-coumaric acid (p-CA) was performed. Experimental designs were carried out to this end. First, a Plackett Burman design was used to choose the important factors that affect p-CA production. Then, a central composite face centered design was used to find the optima of the two major parameters, C/N ratio and pH. Finally, a four-component optimized semi-defined (OSD) medium was developed and experimented in both biphasic and control batch fermentations. In comparison to the results of previous biphasic fermentations work using a classic defined medium (a 2X Yeast Nitrogen Base medium without Amino Acids), OSD medium was 10 times less expensive per litre. At pH 4.5, the final p-CA production in OSD medium was approximately 61% of the p-CA content reached in the classic defined medium. At pH 6.0, the production of p-CA in OSD medium was 55% of the p-CA reached in the YNB medium.
Forced chicory roots (FCR) are the main but also the least valued by-products of Belgian endive culture. However, they contain molecules of interest for industry such as caffeoylquinic acids (CQAs). This study aims to investigate accelerated solvent extraction (ASE) as a green technique to recover chlorogenic acid (5-CQA) and 3,5-dicaffeoylquinic acid (3,5-diCQA), the main CQAs. A D-optimal design was used to determine the influence of temperature and ethanol percentage on their extraction. Optimal extraction conditions were determined using response surface methodology (RSM) and allow the recovery of 4.95 ± 0.48 mg/gDM of 5-CQA at 107 °C, 46% of ethanol and 5.41 ± 0.79 mg/gDM of 3,5-diCQA at 95 °C, 57% of ethanol. The antioxidant activity of the extracts was also optimized by RSM. The highest antioxidant activity was achieved at 115 °C with 40% ethanol (more than 22 mgTrolox/gDM). Finally, correlation between the antioxidant activity and the amount of CQAs was determined. FCR can be a great source of bioactive compounds with potential use as biobased antioxidant.
Pour accélérer la transition écologique de l'agriculture, une valorisation optimale des produits et co-produits végétaux qui en sont issus est nécessaire. Cette étude s'intéresse aux tendances à l’œuvre dans ce domaine, avec un accent particulier mis sur les protéines végétales
La diversification des systèmes de culture vers plus de légumineuses et plantes à fibres est une voie d’amélioration de la résilience économique et climatique des filières végétales. Néanmoins, au delà des contraintes agronomiques, leur développement dépendra en grande partie des opportunités de valorisation qui leur seront offertes.
Étude réalisée par Céresco, Bioeconomy For Change (ex-IAR) et AgroParisTech Innovation, et financée par le ministère de l'Agriculture et de la Souveraineté alimentaire.
Allylation of phenols, a widely used reaction in multistep synthetic pathways, was herein investigated using mechanochemistry. This synthesis was first optimized on vanillin by varying key parameters including both chemical (e.g., stoichiometry, reaction time) and mechanical (e.g., rotational speed, material, size and number of beads, liquid additive) conditions, leading to the isolation of allylated vanillin at the gram scale in excellent yield (95%). The optimized procedure was also successfully implemented to another bio-based phenol of interest, ethyl ferulate (92% isolated yield). The environmental impact of these procedures was compared with more classical in-solution protocols by calculating E factors. When work-up solvents were not taken into account, E factor (sEF) clearly indicated the superiority of the ball-milling approach over the solution-based procedure, underscoring the capacity of ball-mills to drastically reduce the need for “reaction” solvents. On the other hand, when work-up solvents were taken into consideration, E factors (cEF) were in favor of the solvent-based approach, which could be explained by the solvent quantities required to recover the reaction mixture from the ball-mill reactor. Overall, these results highlight (i) the great potential of mechanochemistry to enable the development of both efficient and waste-less allylation of lignin-derived phenolic synthons, and (ii) the need to study higher-scale and continuous mechanochemical processes, such as by using extruders, to further improve efficiency and sustainability of such mechanochemical processes.
Naturally occurring sinapic acid is a valuable synthon for many high-value applications (e.g. cosmetic, pharmaceutic) that can be found in numerous plants, especially Brasiccacea species (e.g. rapeseed, mustard). It has been demonstrated that alkaline extraction of matter rich in sinapic acid resulted in the conversion of sinapic acid into 6-hydroxy-5,7-dimethoxy-2-naphtanoic acid (DMNA). Although DMNA could be a potential alternative to petro-based naphtanoic acid used in polymers, untill now, no reliable (bio)synthetic procedure existed to synthesize it at the preparative-scale. Herein, starting from sinapic acid, we describe a very simple one-pot two-step chemo-enzymatic pathway to DMNA – and reaction intermediaries bislactone (BL) and thomasidioic acid (TA) – at gram scale using a simple filtration as purification step. Green metrics – Process Mass Index and EcoScale – have been determined to assess the sustainability of this new process. Finally, the antiradical activities of DMNA, BL and TA have been evaluated.
A new membrane-based strategy to purify oxidized coenzyme A ((CoAS)2) from adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP) has been developed. Commercially available membranes were screened and studied (permeate flux and overall compounds retention) which allowed the identification of one efficient membrane (GK from Suez Water Technologies & Solutions). Different total compounds concentrations solutions were used in the system in order to find the following working conditions: 4 bars with a total compounds solution of 5.19 g L−1.
Applying these conditions to a dia-filtration set-up allowed us to reach 68% pure (CoAS)2 in 4.8 diafiltration volumes (DV) and a 95% (CoAS)2 purity can be predicted in 8.5 DV. A comparative study of green metrics—i.e. process mass index (PMI)—of the classic chromatography vs the membrane-based one demonstrated the great advantages of the latter in terms of sustainability. This strategy unlocks the access to the essential and central cofactor that is coenzyme A.
The already described one-pot two-step hydration/reduction of levoglucosenone (LGO) into (1R,2S,5R)-6,8-dioxabicyclo[3.2.1]octane-2,4-diol (HO-LGOL) was improved by replacing 50 mol % of Et3N by 5 mol % of K3PO4, a more sustainable base. The sterically hindered diol was then subjected to polycondensations with aliphatic comonomers to prepare new bio-based polyesters that exhibit glass transition (Tg) values between 12 and 54 °C and high thermal stability greater than 200 °C.
Two different strategies were implemented to perform the polymerizations: (1) utilization of aliphatic diacyl chlorides, or (2) a method involving aliphatic diethyl esters in the presence of a metal catalyst. These methods were then subjected to life cycle assessment to study their environmental impacts.
To valorize further the highly valuable bio-based platform (S)-γ-hydroxymethyl-γ-butyrolactone (2H-HBO), whose sustainable kiloscale-synthesis from cellulose-derived levoglucosenone (LGO) has been validated, a mechanochemical strategy was developed to produce new potential bio-based surfactants under solventless conditions. First, the reaction of 2H-HBO with primary or secondary amines was investigated followed by a sulfation reaction with the isolated N-alkyl-amide derivatives to obtain the corresponding N-alkyl sulfated compounds. The latter was then obtained by an optimized one-pot sequential aminolysis–sulfation in a planetary ball mill with excellent efficiency. For the first time, sulfated compounds arising from bio-based/renewable resources were obtained exclusively via a mechanochemical process. As a result, the sulfated derivatives of 2H-HBO were formed quantitatively and isolated in 69–79% overall yields. The critical micelle concentration (CMC) was determined for some of them which exhibited interesting anionic surfactant properties.
Stilbenes are particularly studied for their biological properties. Among them, resveratrol and piceid, present in relatively large quantities in nature, have already demonstrated interesting characteristics. Dimers and oligomers of resveratrol are also very promising, especially, δ-viniferin for which an elegant synthetic method based on the hydrolysis of piceid dimer has been reported. Nevertheless, while the hydrolysis is quantitative, to date, the synthesis of the piceid dimer has only been described in the presence of laccase in toxic methanol and with a relatively average yield (46%). With a view to offering a greener and higher yielding dimerization of piceid, this study aims at (i) conducting the dimerization in the presence of AgOAc in ethanol, (ii) determining the influence of reaction parameters and the optimal conditions by using a Design of Experiment, (iii) assessing the EcoScale and process mass intensity (PMI) of the new procedure, and (iv) comparing it with the laccase-mediated procedure. Data demonstrated that the AgOAc-mediated dimerization of piceid proceeds in higher yield (ca. 64% vs 46%), with a better EcoScale (68 vs 32), while being more economical (PMI score = 2.5 vs 71.4) and using a green solvent (EtOH). Moreover, through this novel route, we were able to identify and fully characterize new dimers that were not reported in the literature so far.
Recently, a renewable five-membered lactone containing citronellol (HBO-citro) was synthesized from levoglucosenone (LGO). A one-pot two-step pathway was then developed to produce a mixture of 5- and 6-membered Lactol-citro molecules (5ML and 6ML, respectively) from HBO-citro. Proton nuclear magnetic resonance (1H NMR) of a mixture of 5ML and 6ML at varying temperatures showed that the chemical shifts of the hydroxyls, as well as the 5ML:6ML ratio, are temperature-dependent. Indeed, a high temperature, such as 65 °C, led to an up-field shielding of the hydroxyl protons as well as a drop in the 5ML:6ML ratio. The monomers 5ML and 6ML were then engaged in polycondensation reactions involving diacyl chlorides.
Renewable copolyesters with low glass transition temperatures (as low as −67 °C) and cross-linked citronellol chains were prepared. The polymers were then hydrolyzed using a commercial lipase from Thermomyces lanuginosus (Lipopan® 50 BG). A higher degradation rate was found for the polymers prepared using Lactol-citro molecules, compared to those obtained by the polycondensation reactions of diacyl chlorides with Triol-citro—a monomer recently obtained by the selective reduction of HBO-citro.
The fabrication of simple and core-shell polymer microparticles is of great importance due to their wide range of industrial applications, such as the food industry, cosmetics, and drug delivery. Regardless of their outstanding advantages, the vast majority of the targeted microparticles are produced using fossil raw materials whose depletion is inevitable, and there is an urgent need to develop innovative classes of sustainable microparticles from renewable resources. Several reviews discussed the common techniques to synthesize polymer microparticles for diverse real-life applications. Nonetheless, no reports were found on the sustainability evaluation of the diverse production methods or the microparticle raw materials and solvents used. In this critical review, the state of the art of polymer microparticles is first described. Next, the sustainability of the common production techniques, including microfluidics, is evaluated based on selected criteria, including waste generation, use of green solvents, atom- and energy efficiency. Furthermore, the challenges of achieving green production are discussed based on three elements: green production process, green raw material, and green solvents. Finally, room for improvement is discussed with highlights on future perspectives, including further investigations that should be accomplished to find renewable substitutes and green up the existing production strategies for better lives for future generations.
Cherry tree branches (Prunus avium var burlat Rosaceae) are agricultural by-products that are often neglected, yet they are rich in phenolic compounds and highly appreciated for their numerous biological activities. Extracts of cherry tree branches were evaluated for their use in cosmetics, particularly for their antioxidant, anti-tyrosinase, and antimicrobial activities. Samples were obtained by accelerated solvent extraction (ASE) at different ethanol percentages and different temperatures. Fourteen phenolic compounds were identified in the extracts by mass spectrometry. Three major compounds were identified (catechin, genistin, and prunin) representing 84 wt% of the total phenolic compounds. Optimal operating conditions maximizing the content of phenolic compounds were determined using a one factor at a time (OFAT) approach (70% aqueous ethanol, 70 °C). The extract obtained under these conditions also showed the highest antioxidant and anti-tyrosinase activities, certainly due to a high catechin content. Although the antimicrobial activities of extracts are less versatile than those of synthetic molecules, they are nonetheless interesting. According to these results, the extracts of cherry tree branches could be used in cosmetics for their interesting properties.
Chlorogenic acids are major phenolic constituents in many herbal medicines and exhibit various bioactivities that explain the growing interest in extracting chlorogenic acids from biomass. In this context, the present study aims to maximize 3-O-Caffeoylquinic acid (3-CQA) and 3,5-O-di-caffeoylquinic acid (3,5-diCQA) contents from forced witloof chicory roots and to analyze the extraction kinetic modelling. First, the solid–liquid ratio, ethanol concentration, extraction time and temperature were studied. The extraction conditions were optimized to maximize the extraction of these compounds. The maximum yields reached 5 ± 0.11 and 5.97 ± 0.30 mg/g dry matter (DM) for 3-O-Caffeoylquinic acid and 3,5-O-di-caffeoylquinic acid, respectively, in less than 6 min at 70 °C. Extraction with water as a solvent was assessed with the aim of proposing a second greener and less-expensive solvent. This extraction is very fast from 90 °C, with a maximum of 6.22 ± 0.18 mg/gDM of 3-O-Caffeoylquinic acid, and instantaneous for 3,5-O-di-caffeoylquinic acid with a maximum of 6.44 ± 0.59 mg/gDM. In the second step, response surface methodology was employed to optimize the ultrasound-assisted extraction of antioxidants. The higher antioxidant activities were found at temperatures from 40 °C and at percentages of ethanol in the range of 35–70%.
This work aims to intensify trans-p-coumaric acid (p-CA) heterologous production. p-CA exhibits antimicrobial properties, low hydrosolubility, and retro-inhibition activity, making its heterologous production limited due to its accumulation in the broth. To overcome these limitations, an in-stream product recovery process (ISPR) is proposed and consists in a liquid-liquid extraction assisted by a hollow fiber membrane contactor. pH, medium composition, and solvent impacts on extraction performances, were investigated prior to the implementation. The coupling of the fermentation and the membrane-assisted extraction was then investigated. Although cells were impaired by shear stress with only 15% of viable cells at the end in the extractive fermentation, the final p-CA concentration was approximatively 89% of the control one, suggesting an intensification of p-CA heterologous production if one factors the proportion of viable cells.
Projections show that the cultivation of microalgae will extend to the production of bio-based compounds, such as biofuels, cosmetics, and medicines. This will generate co-products or residues that will need to be valorized to reduce the environmental impact and the cost of the process. This study explored the ability of lipid-extracted Chlorella vulgaris residue as a sole carbon and nitrogen source for growing oleaginous yeasts without any pretreatment. Both wild-type Yarrowia lipolytica W29 and mutant JMY3501 (which was designed to accumulate more lipids without their remobilization or degradation) showed a similar growth rate of 0.28 h−1 at different pH levels (3.5, 5.5, and 7.5). However, the W29 cell growth had the best cell number on microalgal residue at a pH of 7.5, while three times fewer cells were produced at all pH levels when JMY3501 was grown on microalgal residue. The JMY3501 growth curves were similar at pH 3.5, 5.5, and 7.5, while the fatty-acid composition differed significantly, with an accumulation of α-linolenic acid on microalgal residue at a pH of 7.5. Our results demonstrate the potential valorization of Chlorella vulgaris residue for Yarrowia lipolytica growth and the positive effect of a pH of 7.5 on the fatty acid profile.
Poly-β-hydroxybutyrate (PHB) is a very common bio-based and biocompatible polymer obtained from the fermentation of soil bacteria. Due to its important crystallinity, PHB is extremely brittle in nature, which results in poor mechanical properties with low extension at the break. To overcome these issues, the crystallinity of PHB can be reduced by blending with plasticizers such as ferulic acid derivatives, e.g., bis-O-dihydroferuloyl-1,4-butanediol (BDF). The degradation potential of polymer blends of PHB containing various percentages (0, 5, 10, 20, and 40 w%) of BDF was investigated through chemical, enzymatic and fungal pathways. Chemical degradation revealed that, in 0.25 M NaOH solution, the presence of BDF in the blend was necessary to carry out the degradation, which increased as the BDF percentage increased. Whereas no enzymatic degradation could be achieved in the tested conditions. Fungal degradation was achieved with a strain isolated from the soil and monitored through imagery processing. Similar to the chemical degradation, higher BDF content resulted in higher degradation by the fungus.
Cellulose-derived photocrosslinkable polycarbonates (PCs) with renewable citronellol pendant chains were synthesised through the polycondensation of Triol-citro, a recently developed levoglucosenone-based triol monomer, and dimethoxycarbonyl isosorbide. The polymer structures were unveiled through NMR spectroscopy and four repeating units were identified: three hydroxy-functional linear units (Ln, Lo and Lp) and one dendritic unit (Dq). The relative percentages of the repeating units, as well as the molecular weights of the corresponding polymers, can be finely tuned by varying the catalyst and reaction conditions (i.e., polycondensation temperature and monomer concentration). Thermal analyses demonstrated that the novel PCs exhibited low glass transition temperatures (Tg as low as -72 °C) and good thermal stability (Td5% up to 159 °C). These hydroxy-functionalised PCs are not only fully biobased with a controlled extent of branching, but they also bear citronellol side chains that were successfully crosslinked via ultraviolet irradiation to further control the polymer properties.
Poly(3-hydroxybutyrate), PHB, has gathered a lot of attention for its promising properties—in particular its biobased nature and high biodegradability. Although PHB is prime candidate for the packaging industry, the applications are still limited by a narrow processing window and thermal degradation during melt processing. In this work, three novel additives based on ferulic acid esterified with butanediol, pentanediol, and glycerol (BDF, PDF, and GTF, respectively) were used as plasticizers and antioxidative additives to improve mechanical properties of PHB. Elongation at break up to 270% was obtained in presence of BDF and the processing window was improved nearly 10-fold. The Pawley method was used to identify the monoclinic space group P2 of the BDF. The estimated crystallite size (71 nm) agrees with a crystalline additive. With PHB70BDF30 blends, even higher elongations at break were obtained though dwindled with time. However, these properties could be recovered after thermal treatment. The high thermal stability of this additive leads to an increase in the fire retardancy property of the material, and the phenolic structure induced antioxidant properties to the samples as demonstrated by radical scavenging tests, further highlighting the possibilities of the PHB/additive blends for packaging applications.
The sustainable extraction of secondary metabolites from Brassica agro-industrial by-products often involves the use of high concentrations of ethanol, and/or high temperatures, which tends to decrease the efficiency of protein extraction (yield, profile, etc.). To understand the limits of the combination of these two extraction processes, aqueous ethanol extraction of secondary metabolites (e.g., phenolic compounds and glucosinolates) from Brassica carinata defatted meal was optimized using Response Surface Methodology. The validated models predicted that aqueous ethanol extraction of defatted Carinata meal, with a low aqueous EtOH concentration (22% EtOH) at moderate Te (50 °C), enables the efficient recovery of secondary metabolites (sinapine = 9.12 ± 0.05 mg/gDM, sinigrin = 86.54 ± 3.18 µmol/gDM) while maintaining good protein extractability (59.8 ± 2.1%) from successive alkaline extractions. The evaluation of functional properties of the resulting protein isolates revealed that aqueous extraction, under optimized conditions, improves foaming activity while preserving emulsion ability.
The recent ban of some organic UV-filters – such as oxybenzone or octinoxate – considered toxic for coral reef, has heightened the need for eco-friendly alternatives, especially those synthesized using green approaches that reduce the carbon footprint. In this context, several thiobarbituric acid derivatives were synthetized from bio-based p-hydroxybenzaldehydes (e.g. vanillin, syringaldehyde) through a high-yielding sustainable Knoevenagel condensation, and their UV-filtering activity, stability and antiradical properties were investigated. The results showed promising UVA and blue light coverage over time, as well as competitive EC50 values in comparison to commercial antioxidants (i.e. BHA and BHT). In order to evaluate the potential of these molecules as substitutes to current petroleum-based UV-filters, the potential toxicity and fate in environment of these new compounds were evaluated in silico. This screening did not show a critical potential for toxicity, making them promising candidates for further in vitro and in vivo assessment.
Levoglucosenone (LGO) is a cellulose-derived molecule that is present commercially on a multi-ton/year scale. Taking advantage of the α,β-conjugated ketone of LGO, a new citronellol-containing 5-membered lactone (HBO-citro) was synthesized through a one-pot two-step pathway involving oxa-Michael addition and Baeyer-Villiger oxidation. The solvent-free treatment of HBO-citro with NaBH4 at room temperature led to the full reduction of the lactone moiety which gave a novel fully renewable triol monomer having a citronellol side chain (Triol-citro). Noticeably, by simply changing the reducing agent, temperature and reaction duration, the partial reduction of HBO-citro can be achieved to yield a mixture of 5- and 6-membered Lactol-citro molecules. Triol-citro was chosen to prepare functional renewable polyesters having citronellol pendant chains via polycondensation reactions with diacyl chlorides having different chain lengths. Good thermal stability (Td5% up to 170 °C) and low glass transition temperatures (as low as −42 °C) were registered for the polyesters obtained. The polymers were then hydrolyzed using a commercial lipase from Thermomyces lanuginosus (Lipopan® 50 BG) to assess their biodegradability. A higher degradation profile was found for the polyesters prepared using co-monomers (acyl chlorides) having longer chain lengths. This is likely due to the decreased steric hindrance around the ester bonds which allowed enhanced accessibility of the enzyme.
Using photocatalysis with tetra-n-butylammonium decatungstate (TBADT), alkanes, cyclic acetals, cyclic ethers, formamide and aldehydes were added in a stereoselective way to levoglucosenone (LGO). A hydrogen atom is transferred from the donor compound to the photochemically excited TBADT, and the resulting radicals add onto LGO in a stereoselective way. In the case of the addition of adamantane, two regio-isomers were obtained which form a crystalline solid solution. Cyrene™, obtained by hydrogenation of LGO, was added under the same conditions. In this case, only two of 32 possible isomers of the resulting Cyrene™ dimer were formed. The regio-selectivity of the HAT step is discussed in detail. For this purpose, bond dissociation energies and partial charges have been calculated. Transition state calculations of the radical addition to LGO explain the stereospecificity of this reaction step.
Membrane-based reactive extraction as an in situ product recovery technique is a promising strategy for process intensification, in particular in the case of the bioproduction of organic acids. Reactive extraction allows a high selectivity for the extraction of the targeted acid and the microporous membrane keeps biocatalysts in the aqueous broth while implementing a large liquid-liquid surface area and ensuring a dispersion-free contact, without problems of emulsion formation. This paper deals specifically with the extraction of biobased 3-hydroxypropionic acid using tri-n-octylamine in n-decanol. In order to maintain an effective driving force for 3-HP transfer into the organic phase, this latter was continuously regenerated by recovering the acid in a back-extraction aqueous phase, giving a complete pertraction process. A mass transfer model for this process was developed. It is based on the boundary layer theory and takes into account chemical and physical equilibria of complexation/dissociation and partitioning, species diffusion in the membrane pores and viscosity variations in the organic phase. Viscosity highly depends on acid concentration, increasing up to 50% when 3-HP concentration reaches 28 g.L-1. Thus, it was possible to predict different experimental results with R2 ≥ 0.99, totally neglecting chemical kinetics and interfacial resistance for both extraction and back-extraction steps. The model allows the prediction of extraction kinetics with (1) fixed initial concentrations and (2) with gradual 3-HP feed (mimicking a bioconversion) in transient and steady states coupled with back-extraction (globally also called pertraction). Model based analysis of mass transfer mechanisms led to the construction of a nomogram giving 3-HP stationary concentration in the case of a typical production rate, enabling for example a rapid organic phase selection or membrane sizing.
By-products obtained through the industrial processing of rapeseed and mustard seeds are exploited as feed or methanization. However they contain high added value phenolic compounds, such as sinapic acid and its derivatives, that could be recovered by extraction and purification processes. This review presents the state of the art on such recovery processes. It covers conventional extraction by solvent and emergent extraction processes, namely solvent extraction assisted by ultrasound, microwaves, pressure, electro-technologies or enzymes. Concerning the purification processes, liquid-liquid extraction, adsorption and membrane filtration processes are commonly implemented. This article summarizes the most promising methods and technologies for developing sustainable processes for the recovery of sinapic acid derivatives from rapeseed and mustard seed by-products.
Lignocellulose-derived p-hydroxycinnamic acids possess the photo-responsive reversible α,β-unsaturated ester moiety, a reactive structural feature that functions as the basis of the photo-reversible [2 + 2] cycloaddition reaction. To explore the potential of these naturally occurring compounds in the field of self-healing materials, novel bio-based photo-crosslinkable lignin- and glycerol-derived polyfunctional monomers having cinnamate groups were produced using a sustainable process from vanillin and syringaldehyde, two compounds readily obtained from the oxidation of lignin. Through a Structure–Activity Relationship (SAR) study, the structural design of these bio-based monomers was optimized with regards to the crosslinking/decrosslinking extent and the self-healing capacity of the corresponding polymer material. The lignin- and glycerol-derived tri-functional monomer with 4-O-propyl-ferulate moieties has facilitated the design of a new family of bio-based, environment-friendly and reversible self-healing materials for widespread applications. Computational density-functional theory (DFT) and time-dependent DFT calculations were further used for the verification of the SAR study in terms of dimerization energy of the synthesized monomers.
Light-to-heat conversion materials generate great interest due to their widespread applications, notable exemplars being solar energy harvesting and photoprotection. Another more recently identified potential application for such material is in molecular heaters for agriculture, whose function is to protect crops from extreme cold weather and extend both the growing season and the geographic areas capable of supporting growth, all of which could help reduce food security challenges. To address this demand, a new series of phenolic-based barbituric absorbers of ultraviolet (UV) radiation has been designed and synthesised in a sustainable manner. The photophysics of these molecules has been studied in solution using femtosecond transient electronic and vibrational absorption spectroscopies, allied with computational simulations and their potential toxicity assessed by insilico studies. Following photoexcitation to the lowest singlet excited state, these barbituric absorbers repopulate the electronic ground state with high fidelity on an ultrafast time scale (within a few picoseconds). The energy relaxation pathway includes a twisted intramolecular charge-transfer state as the system evolves out of the Franck-Condon region, internal conversion to the ground electronic state, and subsequent vibrational cooling. These barbituric absorbers display promising light-to-heat conversion capabilities, are predicted to be non-toxic, and demand further study within neighbouring application-based fields.
The simultaneous extraction and enzymatic hydrolysis of sinapine from a mustard residue was designed for the recovery of sinapic acid, a high value-added phenolic acid. An initial screening allowed the identification of sinapoyl esterase activities in commercial enzymatic cocktails (Depol 740 L, Ultraflo XL, Deltazym VR AC-100, Pectinase-PL “Amano”) and in a mono-enzymatic solution of rumen feruloyl esterase. These enzymatic cocktails were not very tolerant to ethanol with a diminution of 70 to 90% of the activity in presence of 10% (v/v) of ethanol. Different extraction processes on mustard bran were designed depending on the solvent compositions (ethanol 70% (v/v), water with or without sinapoyl esterase), pH (4.3, 7 or 12) and temperatures (50, 75 or 100 °C). Their respective efficiencies were discussed. The implementation of Depol 740 L in water allowed to recover 68% of the accessible sinapic acid (25.4 ± 0.1 µmol/g of bran dry matter) in 2h40 min under mild conditions (pH 7, 50 °C). This efficient biocatalytic production of sinapic acid from mustard feedstock using an enzymatic cocktail paves the way for new developments for the design of an industrial process.
Amanita muscaria is the most emblematic mushroom in the popular representation. It is an ectomycorrhizal fungus endemic to the cold ecosystems of the northern hemisphere. The basidiocarp contains isoxazoles compounds that have specific actions on the central nervous system, including hallucinations. For this reason, it is considered an important entheogenic mushroom in different cultures whose remnants are still visible in some modern-day European traditions. In Siberian civilizations, it has been consumed for religious and recreational purposes for millennia, as it was the only inebriant in this region.
The already reported, yet hazardous, Et3N-catalyzed levoglucosenone (LGO) hydration into 1,6-anhydro-3-deoxy-β-D-erythro-hexo-pyranose-2-ulose (LGO-OH) has been greened up by substituting Et3N with K3PO4 and performing the reaction in H2O. Optimal reaction conditions (K3PO4 (0.05 eq.), [LGO] = 0.08 M, 5 h) not only allowed higher yields, but also limited the homocoupling of LGO, a competitive side reaction. A comparative – yet non-comprehensive and perfectible – Life Cycle Assessment (LCA) using the CML 2002 method highlighted the specific impacts where this revisited synthesis outperformed the Et3N-catalyzed one. 1,6-Anhydro-3-deoxy-β-D-erythro-hexo-pyranose-2-ulose was then subjected to a one-pot catalyst- and organic solvent-free Baeyer-Villiger oxidation/rearrangement, without the need to perform acidic hydrolysis, to access 2-deoxy-D-ribonolactone (HO-HBO, 79% yield). To assess the potential of HO-HBO as monomer for the production of novel bio-based polyesters, the latter was finally polymerized in the presence of aliphatic diacyl chlorides to make a proof-of-concept. Resulting polyesters exhibited promising glass transition temperature (Tg) values between -21 and -2 °C and melting temperatures (Tm) from 87 to 144 °C, demonstrating the potential of HO-HBO for the production of sustainable alternatives to current fossil-based polymers.
Hypothesis: The crystallisation of biosourced ferulic acid derivatives - Bis-O-feruloyl-1,4-butanediol (BDF) - in a polylactic acid (PLA) matrix produces thermoplastic elastomeric blends that are transparent and biodegradable. Elastomeric and transparency are controlled by the domain size. PLA-BDF blends up to a threshold BDF concentration providing elastomeric properties show no evidence of BDF crystallisation. Heat treatment weakens the PLA-BDF interaction, give BDF molecules mobility to interact with nearby BDF molecules, leading to BDF nano-crystallisation.
Experiments: PLA-BDF blends were synthesised by hot-melt processing by mixing pure PLA with different concentrations of BDF (0-40 wt%) at 180 °C for 13 minutes. One set of blends was annealed at 50 °C for 24 h and compared with the unannealed set. The BDF crystallisation in the blends is studied by combining SAXS, SEM, XRD and Polarised Optical Microscopy. Monte-Carlo simulations were performed to validate SAXS data analysis.
Findings: Unannealed PLA-BDF blends of up to the threshold of 20 wt% BDF are dominated by the semicrystalline behaviour of PLA, without any trace of BDF crystallisation. Surprisingly, the PLA-BDF 40 wt% blend shows BDF crystallisation in the form of large and nanoscale structures bonded together by weak interparticle interaction. At concentrations up to 20 wt%, the BDF molecules are homogenously dispersed and bonded with PLA. Increasing BDF to 40 wt% brings the BDF molecules close enough to crystallise at room temperature, as the BDF molecules are still bonded with the PLA network.
Annealing of PLA-BDF blends led to BDF nanocrystallisation and self-assembling in the PLA network. Both BDF nanoparticle size and interparticle distance decrease as the BDF concentration increases. However, the number density of BDF nanocrystals increases. The formed BDF nanocrystals have size ranging between 100 and 380 Å with interparticle distance of 120-180 Å. The structure factor and potential mean force confirm the strong interparticle interaction at the higher BDF concentration. Heat treatment weakens the PLA -BDF interaction, which provides mobility to the BDF molecules to change conformation and interact with the nearby BDF molecules, leading to BDF crystallisation. This novel BDF crystallisation and self-assembly mechanism can be used to develop biodegradable shape memory PLA blends for biomedical, shape memory, packaging and energy applications.
Inspired by nature’s photoprotection mechanisms, we report an effective UV-blocking nanomaterial based on diethyl sinapate-grafted cellulose nanocrystals (CNC-DES). The colloidal stability and UV-blocking performance of CNC-DES in aqueous glycerol (a common humectant in petroleum-free cosmetic formulations) and in a commercially-available moisturising cream were studied. Grafting the water-insoluble DES onto CNCs renders it dispersible in these water-based formulations, thanks to the excellent water-dispersibility of CNC nanoparticles. Glycerol dispersions containing 0.1 to 1.5 wt% CNC-DES display very high UV-blocking activity owing to the anti-UV DES moieties anchored onto CNCs. A facial cream blended with 1.5 wt% CNC-DES exhibits an SPF of 5.03, which is higher than a commercially-available sunscreen with the same active ingredient concentration (SPF = 3.84). DPPH radical scavenging assay also showed the antioxidant potential of CNC-DES, albeit coinciding with a significant reduction in antioxidant activity after grafting DES onto CNCs. Cytotoxicity measurements revealed the CNC-DES not to cause significant cytotoxicity to murine fibroblast cells after 24 h of exposure. Overall, CNC-DES exhibits strong anti-UV and antioxidant properties and is water-dispersible, biocompatible, non-greasy, and light-weight. This study demonstrates the exceptional potential of DES-grafted CNCs as nature-inspired UV-filters in the next generation of cosmetic formulations, including those for sensitive skins.
New Book Chapter !
Summer is not only the time for everyone to enjoy the sun; it also gets us excited about the mouthwatering smoky taste of barbecued food. Although everyone agrees that charcoal- and wood-grilled food is delicious, few really appreciate the chemistry behind the great smoky flavour of barbecued meat. When wood and charcoal burn, cellulose, hemicelluloses and lignins are thermally degraded. Lignins are responsible for the smoky flavour; indeed, a variety of phenolic compounds are generated through the oxidative degradation of lignins via pyrolysis. Wood and charcoal have been proven to play a crucial role in the production of the smoky taste and smell; however, the glycation reactions sometimes called Maillard reactions also strongly contribute to the delicious flavour of grilled food. Moreover, these also provide the grilled meat with the characteristic brown colour. Although wood- and charcoal-grilling brings delicious smoky flavour and smell to the meat, it can also generate harmful chemicals.
The homopolymerization in basic conditions of the recently reported bis(γ-lactone), 2H-HBO-HBO, is herein described for the first time. The solvent-free polymerization of this pentafunctional levoglucosenone (LGO) derivative afforded fully renewable poly(vinyl-ether lactone) copolymers with a highly hyperbranched structure. This investigation stemmed from the polycondensation trials between 2H-HBO-HBO and di(methyl carbonate) isosorbide (DCI) that failed to give the anticipated polycarbonates. Such unexpected behavior was ascribed to the higher reactivity of the 2H-HBO-HBO hydroxy groups towards its α,β-conjugated endocyclic C = C, rather than the DCI methylcarbonate moieties. The different mechanistic scenarios involved in 2H-HBO-HBO homopolymerization have been addressed and a possible structure of poly(2H-HBO-HBO) was suggested. Furthermore, the readily accessible (S)-γ-hydroxymethyl-α,β-butenolide (HBO) was also polymerized for the first time at a relatively large-scale, without any prior modification, resulting in a new hyperbranched polymer with an environmental factor (E factor) ∼ 0. These new HBO-based polymers have a great potential for industrial-scale production due to their interesting properties and easy preparation via a low-cost, green and efficient process.
Liquid chromatography - mass spectrometry (LC-MS) experiments were used to qualitatively and semi-quantitatively monitor the impact of bead milling and the influence of the nature of the extraction solvents, Bligh and Dyer (B&D) versus n-heptane, on the composition of the structural lipids extracted from the microalgae Microchloropsis gaditana (M. gaditana).
In concrete technology, superplasticizers (SPs) are commonly used to reduce water content in concrete admixtures. Although most of them are fossil fuel-based, some derive from lignosulfonates (LS), that are sustainable and environmentally-friendly polyphenolic crosslinked polymers. Indeed, LS are an inexpensive and abundant raw material that contains a variety of functional groups including hydroxyls which can be involved in a wide range of chemical modifications to finely tune the physico-chemical properties of the material. This review presents: (1) the current SPs and their mechanism of adsorption and dispersion as admixtures to improve the properties of fresh concrete (e.g., workability, fluidity, setting time and water reducing ability) and that of hardened concrete (e.g., compressive and flexural strength), (2) LS origin and structure, (3) the various LS functionalization methods reported in the literature since 2000, and (4) their corresponding applications in the different fields such as water depollution, dispersant, superadsorbant, antioxidant, material replacement, and more specifically as water reducers for concrete. A special focus is made on the cement-SPs interactions and the impact of the modified-LS structures on the efficiency of concrete. This review aims at demonstrating that, in the context of green chemistry, biorefinery and bioeconomy, sustainable chemical modification of low cost and abundant LS is a worthwhile approach to design materials that find applications in critical industries such as the concrete sector.
A bioreactor using membrane technologies was used to demonstrate the feasibility of in-situ bio-methanation coupled to industrial wastewater treatment for biogas upgrading. High biogas productivity (1.7 Nm3Biogas/m3Bioreactor/day) with high CH4 content (97.9%) was reached. In-situ bio-methanation did not affect the COD removal efficiency of anerobic digestion (>94%). Process resilience has been tested for both substrate overload and H2 intermittence injection. Recovery of high CH4 content after 7 days without H2 injection occurred within few hours. Influence of microbial community has been studied showing that both hydrogenotrophic and homoacetogenic-acetoclastic pathways were involved.
p-coumaric acid (p-CA) can be produced from D-glucose by an engineered S. cerevisiae strain. p-CA has antimicrobial properties and retro-inhibition activity. Moreover, p-CA is a hydrophobic compound, limiting its accumulation in fermentation broth. To overcome these issues all at once, a liquid-liquid extraction in-situ product recovery process using oleyl alcohol as extractant has been implemented in order to continuously extract p-CA from the broth. Media and pH impacts on strain metabolism were assessed, highlighting p-CA decarboxylase endogenous activity. Biphasic fermentations allowed an increase in p-CA respiratory production rates at both pH assessed (13.65 and 9.45 mg.L-1.h-1 at pH 6 and 4.5, respectively) compared to control ones (10.5 and 7.5 mg.L.-1.h-1 at pH 6 and 4.5, respectively). Biphasic fermentation effects on p-CA decarboxylation were studied showing that continuous removal of p-CA decreased its decarboxylation into 4-vinylphenol at pH 4.5 (57 mg.L-1 in biphasic fermentation vs 173 mg.L-1 in control one).
Plastic waste, which is one of the major sources of pollution in the landfills and oceans, has raised global concern, primarily due to the huge production rate, high durability, and the lack of utilization of the available waste management techniques. Recycling methods are preferable to reduce the impact of plastic pollution to some extent. However, most of the recycling techniques are associated with different drawbacks, high cost and downgrading of product quality being among the notable ones. The sustainable option here is to upcycle the plastic waste to create high-value materials to compensate for the cost of production. Several upcycling techniques are constantly being investigated and explored, which is currently the only economical option to resolve the plastic waste issue. This review provides a comprehensive insight on the promising chemical routes available for upcycling of the most widely used plastic and mixed plastic wastes. The challenges inherent to these processes, the recent advances, and the significant role of the science and research community in resolving these issues are further emphasized.
Cannabis sativa L. is a controversial crop due to its high tetrahydrocannabinol content varieties; however, the hemp varieties get an increased interest. This paper describes (i) the main categories of phenolic compounds (flavonoids, stilbenoids and lignans) and terpenes (monoterpenes and sesquiterpenes) from C. sativa by-products and their biological activities and (ii) the main extraction techniques for their recovery. It includes not only common techniques such as conventional solvent extraction, and hydrodistillation, but also intensification and emerging techniques such as ultrasound-assisted extraction or supercritical CO2 extraction. The effect of the operating conditions on the yield and composition of these categories of phenolic compounds and terpenes was discussed. A thorough investigation of innovative extraction techniques is indeed crucial for the extraction of phenolic compounds and terpenes from cannabis toward a sustainable industrial valorization of the whole plant.
Handbook of Molecular Gastronomy: Scientific Foundations and Culinary Applications presents a unique overview of molecular gastronomy, the scientific discipline dedicated to the study of phenomena that occur during the preparation and consumption of dishes. It deals with the chemistry, biology and physics of food preparation, along with the physiology of food consumption. As such, it represents the first attempt at a comprehensive reference in molecular gastronomy, along with a practical guide, through selected examples, to molecular cuisine and the more recent applications named note by note cuisine. While several books already exist for a general audience, either addressing food science in general in a "light" way and/or dealing with modern cooking techniques and recipes, no book exists so far that encompasses the whole molecular gastronomy field, providing a strong interdisciplinary background in the physics, biology and chemistry of food and food preparation, along with good discussions on creativity and the art of cooking.
Agriculture in Champagne owes its development to the determination of people and their ability to implement technical progress, work together to adapt to changes. The strong dynamic of the agricultural cooperative has been crucial in this exceptional development, in terms of agriculture, industrial processing and innovation. The Bazancourt-Pomacle biorefinery is both the result and the symbol of the determination of local farmers to develop new regional outlets by using cutting-edge technologies. The success of the site, considered as “the archetype of a territorial biorefinery,” is a perfect illustration of how, through innovation, weaknesses can become strengths. For this constantly evolving model, 2021 is, with the growing importance of bioeconomy, a new tipping point for the Bazancourt-Pomacle biorefinery.
The response surface methodology (RSM) is a relevant mathematical and statistical tool for process optimization. A state of the art on the optimization of the extraction of phenolic compounds from Brassica has shown that this approach is not sufficiently used. The reason for this is certainly an apparent complexity in comparison with the implementation of a one-factor-at-a-time (OFAT) optimization. The objective of this chapter is to show how one implement the response surface methodology in a didactic way on a case study: the extraction of sinapine from mustard bran. Using this approach, prediction models have been developed and validated to predict the sinapine content extracted as well as the purity of the extract in sinapine. The methodology presented in this chapter can be reproduced on any other application in the field of process engineering.
Sinapic acid (SinA) and corresponding esters are secondary metabolites abundantly found in plants of Brassica family. Belonging to the family of p-hydroxycinnamic acids, SinA and its esters analogues are present in different plant parts and involved in multiple biological processes in planta. Moreover, these metabolites are also found in relatively large quantities in agro-industrial wastes. Nowadays, these metabolites are increasingly drawing attention due to their bioactivities which include antioxidant, anti-microbial, anti-cancer and UV filtering activities. As a result, these metabolites find applications in pharmaceutical, cosmetic and food industries. In this context, this article reviews innate occurrence, biosynthesis, accessibility via chemical synthesis or direct extraction from agro-industrial wastes. Biological activities of SinA and its main corresponding esters will also be discussed.
Grafting novel and nature-inspired phenolic esters onto cellulose nanocrystals (CNCs) provides nanofibers with excellent protection against UV radiation when incorporated into a polymer matrix. In this work, CNCs decorated with a novel UV-absorbing phenolic diester (CNC-diethyl ferulate or CNC-DEF) obtained via a click-type copper-catalyzed azide/alkyne cycloaddition reaction were incorporated into a polyvinyl alcohol (PVA) matrix to produce transparent films with excellent photostability and UV-absorbing properties. PVA films filled with 20 wt % CNC-DEF exhibited complete UV protection (0% transmittance) and high transparency in the visible region (70–90% transmittance). In contrast, PVA films loaded with the pristine CNCs do not show any UV-shielding properties. Importantly, the grafting of DEF moieties on CNCs significantly aids the dispersion of the phenolic diester in the aqueous PVA matrix, which was not achieved with DEF blended with PVA. Mechanical tests also show that the addition of 20 wt % CNC-DEF in PVA increases the tensile strength and modulus by 91 and 150%, respectively, relative to neat PVA. The oxygen barrier properties of the composite film also improve with CNC-DEF addition. This study shows the great potential of the phenolic-ester-decorated CNCs as dispersible, multifunctional UV-absorbing nanoreinforcements in PVA films for industrial and packaging applications.
A pilot-scale anaerobic membrane bioreactor (AnMBR) was designed and optimized for the treatment of real distillery wastewater. A low hydraulic retention time of 3.5 days was reached after only 3 weeks. The AnMBR could treat up to 3.97 gCOD/L/day with high biogas production at 1.36 NLbiogas/Lbioreactor/day. The performances of an AnMBR and an anaerobic packed-bed bioreactor for treating the same wastewater were compared. The AnMBR had a shorter start-up period (21 days), a higher COD removal efficiency (96.9 %), and higher stability and methane production (0.26 LCH4/gCODinput), indicating the interest of investigating AnMBR industrialization. The membrane performance was also studied, demonstrating a long cleaning cycle interval of at least 44 days. The transmembrane pressure and Food-to-Microorganism ratio were defined to minimize membrane fouling without affecting the anaerobic digestion performance.
The O-glycosylation of resveratrol increases both its solubility in water and its bioavailability while preventing its oxidation, allowing a more efficient use of this molecule as a bioactive ingredient in pharmaceutical and cosmetic applications. Resveratrol O-glycosides can be obtained by enzymatic reactions. Recent developments have made it possible to selectively obtain resveratrol α-glycosides from the β-cyclodextrin–resveratrol complex in water with a yield of 35%. However, this yield is limited by the partial hydrolysis of the resveratrol glycosides produced during the reaction. In this study, we propose to intensify this enzymatic reaction by coupling the enzymatic reactor to a membrane process. Firstly, membrane screening was carried out at the laboratory scale and led to the choice of a GE polymeric membrane with a cut-off of 1 kDa. This membrane allowed the retention of 65% of the β-cyclodextrin–resveratrol complex in the reaction medium and the transfer of 70% of the resveratrol α-O-glycosides in the permeate. In a second step, this membrane was used in an enzymatic membrane reactor and improved the yield of the enzymatic glycosylation up to 50%.
The current cosmetic and nutraceutical markets are characterized by a strong consumer demand for a return to natural products that are less harmful to both the consumers and the environment than current petrosourced products. Phloretin, a natural dihydrochalcone (DHC) found in apple, has been widely studied for many years and identified as a strong antioxidant and anti-tyrosinase ingredient for cosmetic formulations. Its low concentration in apples does not allow it to be obtained by direct extraction from biomass in large quantities to meet market volumes and prices. Moreover, its remarkable structure prevents its synthesis through a green process. To overcome these issues, the synthesis of phloretin analogs appears as an alternative to access valuable compounds that are potentially more active than phloretin itself. Under such considerations, 12 chalcones (CHs) and 12 dihydrochalcones (DHCs) were synthesized through a green Claisen–Schmidt condensation using bio-based reagents. In order to evaluate the potential of these molecules, radical scavenging DPPH and anti-tyrosinase tests have been conducted. Moreover, the UV filtering properties and the stability of these analogs towards UV-radiations have been evaluated. Some molecules showed competitive antioxidant and anti-tyrosinase activities regarding phloretin. Two compounds in particular showed EC50 lower than phloretin, one chalcone and one dihydrochalcone.
Thanks to its remarkable properties such as sustainability, compostability, biocompatibility, and transparency, poly-l-lactic acid (PLA) would be a suitable replacement for oil-based polymers should it not suffer from low flexibility and poor toughness, restricting its use to rigid plastic by excluding elastomeric applications. Indeed, there are few fully biobased and biodegradable transparent elastomers–PLA-based or not–currently available. In the last decades, many strategies have been investigated to soften PLA and enhance its toughness and elongation at break by using plasticizers, oligomers, or polymers.
This work shows how a ferulic acid-derived biobased additive (BDF) blends with a common rigid and brittle commercial grade of polylactic acid to provide a transparent non-covalently cross-linked elastomeric material with shape memory behavior exhibiting an elongation at break of 434% (vs 6% for pristine PLA). Through a structure–activity relationship analysis conducted with BDF analogues and a modeling study, we propose a mechanism based on π–π stacking to account for the elastomeric properties. Blending ferulic acid derivatives with polylactic acid generates a new family of fully sustainable transparent elastomeric materials with functional properties such as shape memory.
A sequence from the complete genome of Pseudomonas aeruginosa strain Pa1242 was identified to code for a potential new Cyclohexanone Monooxygenase (CHMO). The latter was discovered using the Basic Alignment Search Tool (BLAST) with the DNA sequence of the CHMO from Acinetobacter sp. NCIB 9871 as parent sequence considering that this enzymes family maintains a relatively high query cover (>95%) and identity percentage (>50%) among many different microorganisms. This was confirmed by the bioconversion of cellulose-based green solvent CyreneTM into key precursor (S)-γ-hydroxymethyl-butyrolactone (2H-HBO) using a new strain of E. coli BL21(DE3) containing a plasmid designed for the overexpression of the unprecedent CHMO (pLM7). Besides confirming the CHMO activity of this novel sequence, this bioconversion allows the obtention of 2H-HBO while maintaining the naturalness of the process. The optimal culture conditions were assessed through a Design of Experiment, and the control of the pH and O2 level allowed to reach working concentration of 20 g/L of CyreneTM with total conversion and a productivity rate of 401 ± 36 mg/L/h.
This study reports on the optimization of the operating conditions using response surface methodology and a comparative study of three promising technologies of cell disruption (bead milling, microwaves and ultrasound) to increase the lipid extraction from Nannochloropsis oceanica, Nannochloropsis gaditana and Tetraselmis suecica. Central composite designs were used for the optimization of ultrasound and microwave processes. The performance of the cell disruption processes in breaking down microalgae cells is dependent on the strain of microalgae. Microwaves (91 °C for 25 min) were the most efficient for the recovery of lipids from N. oceanica, reaching a lipid content of 49.0% dry weight. For N. gaditana, ultrasound process (80% of amplitude for 30 min) was the most efficient in terms of lipid recovery (21.7% dry weight). The two aforementioned processes are ineffective in disturbing T. suecica whatever the operating conditions used. Only the bead milling process at low flow feed rate with 0.4 mm zirconia beads made it possible to extract 12.6% dry weight from T. suecica. The fatty acid profiles of N. oceanica and T. suecica are affected by the cell disruption process applied. The calculation of specific energy consumption has shown that this criterion should not be neglected. The choice of the most suitable cell disruption process can be defined according to numerous parameters such as the microalgae studied, the total lipid extracted, the fatty acids sought, or the energy consumption.
The usage of renewable resources has become a hot topic upon the rising global awareness against fossil feedstock consumption. Lignin, the 2nd most abundant natural polymer on Earth, is an aromatic biomacromolecule that holds a tremendous potential for the synthesis of biobased materials. The production of monomers and polymers from lignin has been investigated for years and keeps on-expanding, as proven by the flourishing literature. However, the sustainability of the chemical synthesis has not been systematically analyzed. Herein, green chemistry plays a vital role in this area and provides several tools to design eco-friendly production methods. This critical review first describes the preeminent approaches for the synthesis of biobased monomers and polymers from lignin-derived compounds. In the second part, the “greenness” aspects of the 175 key monomer synthesis methods and 32 polymerization methods are evaluated based on selected criteria, including waste generation, atom efficiency, energy efficiency, usage of safer solvents and biocatalytic methodology. The accessible green metrics, such as environmental factor (E factor) and atom economy are calculated to measure the greenness and to provide a quantitative base for strategic decisions. Furthermore, this study provides insights for the improvement opportunities and lights up the room for further developments. This review, aiming at scientists, industries and investors, strives to provide a critical outlook for the existing synthetic methods and motivates researchers to call for the integration of sustainability factors.
Considering the drawbacks associated with the fossil-based molecules, polymers and materials, lignin has acquired immense popularity owing to its distinct advantages. However, till date it has not been widely commercialized to produce fossil replacements mainly due to its complex structure and purification hassle. Constant research is going on to discover ways to depolymerize lignin to produce various aromatic chemicals. This highlight review summarizes the key investigations carried out in the field of lignin valorization, purification and the valuable products generated from lignin.
The aim of this paper is to study the effect of the pH on the extraction of sinapic acid and its derivatives from mustard seed meal. Solutions of acidic pH (pH 2), basic pH (pH 12) and distilled water (uncontrolled pH ~ 4.5) were tested at different percentages of ethanol. The maximum extraction yield for sinapic acid (13.22 µmol/g of dry matter (DM)) was obtained with a buffered aqueous solution at pH 12. For ethyl sinapate, the maximum extraction yield reached 9.81 µmol/g DM with 70% ethanol/buffered aqueous solution at pH 12. The maximum extraction yield of sinapine (15.73 µmol/g DM) was achieved with 70% ethanol/buffered aqueous solution at pH 2. The antioxidant activity of each extract was assessed by DPPH assay; the results indicated that the extracts obtained at pH 12 and at low ethanol percentages (<50%) exhibit a higher antioxidant activity than extracts obtained at acidic conditions. Maximum antioxidant activity was reached at pH 12 with buffer solution (11.37 mg of Trolox Equivalent/g DM), which confirms that sinapic acid-rich fractions exhibit a higher antioxidant activity. Thus, to obtain rich antioxidant extracts, it is suggested to promote the presence of sinapic acid in the extracts.
This paper focuses on developing a sustainable and integrated process for the biocatalytic extraction of sinapic acid from the waste biomass of oleaginous “oil-bearing” seeds. Using an optimized chemo-enzymatic technique, sinapine was effectively liberated from mustard bran and then completely hydrolyzed into sinapic acid. Several parameters were optimized to release sinapic acid (e.g., mustard species, extraction methods, mustard production dates, ethanol concentration, solids loading, extraction time and enzyme type or concentration). Subsequently, an integrated bioprocess was developed and scaled up guided. The results revealed that the biomass type or source and the enzyme used can substantially impact the release of sinapic acid, and overall cost, respectively. For the Canadian lot of crude mustard bran, ~10 mg of sinapic acid per g mustard bran was successfully extracted, along with 43 mg total phenolics per g mustard bran and 71 mg sugars per g mustard bran. Lastly, supplementary portions of the biomass (i.e., lipids) were also discussed for their applicability as value added products.
The sparsity of efficient commercial ultraviolet-A (UV-A) filters is a major challenge toward developing effective broadband sunscreens with minimal human- and eco-toxicity. To combat this, we have designed a new class of Meldrum-based phenolic UV-A filters. We explore the ultrafast photodynamics of coumaryl Meldrum, CMe, and sinapyl Meldrum (SMe), both in an industry-standard emollient and on a synthetic skin mimic, using femtosecond transient electronic and vibrational absorption spectroscopies and computational simulations. Upon photoexcitation to the lowest excited singlet state (S1), these Meldrum-based phenolics undergo fast and efficient nonradiative decay to repopulate the electronic ground state (S0). We propose an initial ultrafast twisted intramolecular charge-transfer mechanism as these systems evolve out of the Franck–Condon region toward an S1/S0 conical intersection, followed by internal conversion to S0 and subsequent vibrational cooling. Importantly, we correlate these findings to their long-term photostability upon irradiation with a solar simulator and conclude that these molecules surpass the basic requirements of an industry-standard UV filter.
Lignin is the principal natural source of phenolics but its structural complexity and variability make it difficult to valorize through chemical depolymerization approaches. White rots are one of the rare groups of organisms that are able to degrade lignin in ecosystems. This biodegradation starts through extracellular enzymes producing oxidizing agents to depolymerize lignin and continue with the uptake of the generated oligomers by fungal cells for further degradation. Phanerochaete chrysosporium is one of the most studied species for the elucidation of these biodegradation mechanisms.
Although the extracellular depolymerization step appears interesting for phenolics production from lignin, the uptake and intracellular degradation of oligomers occurring in the course of the depolymerization limits its potential. In this study, we aimed at inhibiting the phenolics uptake mechanism through metabolic inhibitors to favor extracellular oligomers accumulation without preventing the ligninases production that is necessary for extracellular depolymerization. The use of sodium azide confirmed that an active transportation phenomenon is involved in the phenolics uptake in P. chrysosporium. A protocol based on carbonyl cyanide m-chlorophenyl hydrazone enabled reaching 85% inhibition for vanillin uptake. This protocol was shown not to inhibit, but on the contrary, to stimulate the depolymerization of both dehydrogenation polymers (DHPs) and industrial purified lignins.
Upon the raising of environmental awareness, the transition from unsustainable polymers based on fossil resources to sustainable bio-based materials has become a hot topic. Since then, researchers are developing new monomers derived from natural resources to meet the global need in commodity polymers and to replace those based on fossil feedstock. Levoglucosenone (LGO) is a readily accessible chiral molecule from the acid-catalyzed flash pyrolysis of cellulose that can be used as a versatile platform for a wide range of high value-added compounds. This chapter focuses on the new, yet rapidly evolving, field of LGO-derived monomers and their utility in the synthesis of polymers via different polymerization methods. Special considerations are given to the evaluation of the monomer syntheses and polymerization processes under the scope of green chemistry. The discussion is supported by the measurement of both atom economy and E factor, in order to assess the sustainability, as well as to provide a framework that allows the comparison between different approaches.
This work reports on a solvent selection for the liquid-liquid extraction of p-coumaric acid produced by an engineered strain of Saccharomyces cerevisiae. The solvent selection is a key point of liquid-liquid extraction processes and this work describes a simple strategy to choose a suitable solvent for an in situ or in stream product recovery (ISPR) process during bioconversion. ISPR processes allow to limit the inhibition caused by end-products accumulation in the fermentation medium.
The strategy consists in scoring different solvents based on different criteria weighted according to their significance for the process. Extraction performance, solvent biocompatibility and compatibility with materials, were chosen as essential criteria and the first two were assessed experimentally using distribution coefficients and flow cytometry, respectively. Following this first step, three solvents were selected as candidates for the process of interest and ranked according to the process needs using secondary criteria, namely safety, sourcing and price. Finally, oleyl alcohol obtained the highest score and was therefore considered as the most suitable candidate for an ISPR process with the aim of continuously extracting p-coumaric acid from the fermentation medium. This work is a first step towards the implementation of integrated extractive bioconversion for the production of bio-based molecules such as p-hydroxycinnamic acids and derivatives.
The quite recent, yet quickly expanding, norbornene-levoglucosenone-based monomers family was extended to include a novel bi-functional methacrylate monomer that can be readily synthesized through a chemo-enzymatic pathway. The norbornene moiety was selectively polymerized via ring-opening metathesis polymerization (ROMP) under ambient conditions where Cyrene™ was explored for the first time as a green bio-alternative organic solvent for ROMP reactions. The activity of the metathesis catalysts was finely tuned in Cyrene™, versus common and toxic solvents such as dichloromethane, resulting in highly thermostable functional polymers with Td5% up to 401 °C and Tg of −16.8 °C.
Acrylates and polyacrylates have been produced massively due to their interesting application like Plexiglas. However, the contemporary issues of fossil depletion associated to climate change have raised serious concerns. As a result, utilization of renewable sources such as lignocellulosic material and the development of greener processes have been investigated intensively. Herein, we review the preparation of competitive (meth)acrylates and the corresponding polymers made from bio-renewable sources with a specific focus on lignocellulose. While covering a few family of biosynthon to produce acrylates through different synthetic pathways, we also approach the promising properties of the resulting materials.
p‐Hydroxycinnamic acids (i.e. , p‐coumaric, ferulic, sinapic, and caffeic acids) are phenolic compounds involved inter alia in the biosynthesis pathway of lignin. These naturally occurring molecules not only exhibit numerous attractive properties, such as antioxidant, anti‐UV, and anticancer activities, but they also have been used as building blocks for the synthesis of tailored monomers and functional additives for the food/feed, cosmetic and plastics sectors. Despite their numerous high value‐added applications, the sourcing of p‐hydroxycinnamic acids is not ensured at the industrial scale except for ferulic acid, and their production cost remains too high for commodity applications. These compounds can be either chemically synthesized, extracted from lignocellulosic biomass, and recently their production through bioconversion emerged. Herein we will discuss the different strategies described in the literature to produce these valuable molecules.
Glucosinolates (GSLs) are secondary plant metabolites abundantly found in plant order Brassicales. GSLs are constituted by an S-β-d-glucopyrano unit anomerically connected to O-sulfated (Z)-thiohydroximate moiety. The side-chain of the O-sulfate thiohydroximate moiety, which is derived from a different amino acid, contributes to the diversity of natural GSL, with more than 130 structures identified and validated to this day. Both the structural diversity of GSL and their biological implication in plants have been biochemically studied. Although chemical syntheses of GSL have been devised to give access to these secondary metabolites, direct extraction from biomass remains the conventional method to isolate natural GSL. While intact GSLs are biologically inactive, various products, including isothiocyanates, nitriles, epithionitriles, and cyanides obtained through their hydrolysis of GSLs, exhibit many different biological activities, among which several therapeutic benefits have been suggested. This article reviews natural occurrence, accessibility via chemical, synthetic biochemical pathways of GSL, and the current methodology of extraction, purification, and characterization. Structural information, including the most recent classification of GSL, and their stability and storage conditions will also be discussed. The biological perspective will also be explored to demonstrate the importance of these prominent metabolites.
Faced with the increasing demand from both the cosmetic industries and consumers for bio-based, safe and natural skin products, sinapoyl malate, widely described for its UV protection in plants, appears to be an excellent alternative to substitute chemical filters in sunscreens. Unfortunately, the only synthetic routes described in the literature were not only tedious but also exhibit a strong negative environmental impact, thus seriously limiting the industrialization and commercialization of sinapoyl malate. Herein, a shorter and greener synthetic pathway involving Meldrum’s acid opening with unprotected naturally occurring hydroxy-acids and its subsequent Knoevenagel-Doebner condensation with biomass-derived p-hydroxybenzaldehydes was designed and developed.
This two-step procedure, whom sustainability has been assessed using green metrics (atom economy (AE), process atom economy (PAE), E-factor and LCA), is a great alternative to the already reported procedures and allows the access to sinapoyl malate and several analogs in average to good yield. The study of the anti-UV properties, stability against UV radiation, radical scavenging and antimicrobial activities of the targets revealed attractive properties as photostable UV filters, antioxidants and preservatives. Moreover, the water solubility brought by the free carboxylic acids facilitates the incorporation of these molecules in cosmetic formulations. Finally, their innocuousness toward endocrine disruption was demonstrated.
New nature‐inspired and plant‐derived p‐hydroxycinnamate esters and p‐hydroxycinnamate diesters provide excellent protection against UV radiation when incorporated into a matrix. Herein, we report an efficient and sustainable pathway to graft these phenolic compounds onto cellulose nanocrystals via click‐type copper‐catalyzed azide/alkyne cycloaddition (CuAAC) reaction. The successful grafting of the phenolic esters on CNC surface was evidenced by a range of chemical analyses and the degree of substitutions (DS) of the CNC were found to depend on the structure of the phenolic ester grafted. Moreover, not only aqueous suspensions of the phenolic ester‐grafted CNCs strongly absorb in both the UVA and UVB regions, but they also exhibit average to very high photostability. Their large spectrum UV‐absorbing properties and their stability upon exposure to UV are highly influenced by the structure of the phenolic ester, particularly by the extra ester group in p‐hydroxycinnamate diesters. These findings undoubtedly demonstrate that cellulose nanocrystals decorated with such plant‐derived and nature‐inspired phenolic esters are promising sustainable nanomaterials for anti‐UV applications.
The application of food processes can lead to a modification of both the structure and the activities of flavonoids. In this article, the effect of heat treatment and exposure to light on the antioxidant activity of 6 model flavonoid solutions (rutin, naringin, eriodictyol, mesquitol, luteolin, and luteolin 7-O-glucoside) was studied. The evolution of the antioxidant activity measured after heat treatment of 130 °C at 2 h and an exposure to visible light for 2 weeks is measured by the ABTS (2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) method and represented by a new parameter called ΔTEAC. The model solution of Mesquitol showed the highest increase in ΔTEAC after a heat treatment, a value of 200 mM was obtained. The increase in ΔTEAC is always greater with thermal treatment than with light exposure. Thus, temperature and light lead to different degradation pathways of the flavonoid. In vivo measurements were carried out with solutions of naringin, erodictyol, and luteolin 7-O-glucoside. Heated solutions of flavonoids do not exhibit toxicity on cells. The specific activities of superoxide dismutase and glutathione peroxide have been determined and have shown an increased impact on the potential anti-cancer of these solutions by enhancing their cellular antioxidant activity, as well as modulation of the oxidative stress.
Levoglucosenone (LGO) is a cellulose-derived and commercially available platform molecule that is produced at an industrial scale. LGO contains a highly reactive double bond that was used to produce two isomers of norbornene-containing LGO monomers, endo-N-LGO (1) and exo-N-LGO (2). Furthermore, Baeyer-Villiger oxidation of 1 was performed to yield a highly-valuable chiral monomer, endo-N-HBO (3). The norbornene moiety of the prepared monomers was readily polymerized by ring-opening metathesis polymerization (ROMP) in the presence of GI catalyst to access highly thermostable polymers with Td5% up to 360 °C in the case of N-LGO-based polymers and Td5% in the range of 374-380 °C when 3 was polymerized, such range of Td5% being the highest reported up-to-date for the LGO-derived polymers. The effect of monomer concentration over the polymerization process was studied and showed that 4 M solutions lead to a better monomer conversion while preserving the control over the polymer structure and reducing the environmental factor (E factor). GI was found active in the ROMP of 3 without the need of protecting the hydroxy group and thus leading to pendent hydroxy functional polymers. Furthermore, for the first time, copolymers containing both LGO and HBO reactive moieties were prepared by random copolymerization of 1 and 3.
In 2021, Hawaii will permanently ban the use and sale of octinoxate-based sunscreens as studies have shown serious impacts of such UV filters on the coral reef. This ban, which could be generalized to other countries, highlights the extreme need to offer alternative UV filters that are not only effective in terms of sun protection, but also healthy with regards to human health and the environment. In this context, a wide library of p-hydroxycinnamic esters deriving from naturally occurring sinapic acid has been synthesized using a Knoevenagel–Doebner condensation. The UV filtering activities as well as the antioxidant properties of these sinapic acid esters were then investigated. The results showed promising UVB protection and antioxidant efficacy. A Structure–Activity Relationship (SAR) study on the sinapic acid esters highlighted the need of a free phenol to, as expected, observe antioxidant activity, but also to obtain a higher intensity of protection. Moreover, the nature of the ester moiety also proved to be a key structural feature for the UV absorbance, as higher steric hindrance on the ester moiety leads to more active compounds. The judicious structural design of sinapic esters thus provides promising compounds combining UV protection and antioxidant activity.
Sinapoyl malate is a natural plant sunscreen molecule which protects leaves from harmful ultraviolet radi‐ ation. Here, the ultrafast dynamics of three sinapoyl malate derivatives, sinapoyl L‐dimethyl malate, sinapoyl L‐diethyl malate and sinapoyl L‐di‐ t ‐butyl malate, have been studied us‐ ing transient electronic absorption spectroscopy, in a dioxane and methanol solvent environment to investigate how well pre‐ served these dynamics remain with increasing molecular com‐ plexity. In all cases it was found that, upon photoexcitation, deactivation occurs via a trans‐cis isomerisation pathway within ∼ 20‐30 ps. This cis photoproduct, formed during photodeac‐ tivation, is stable and longed‐lived for all molecules in both solvents. The incredible levels of conservation of the isomerisa‐ tion pathway with increased molecular complexity demonstrate the efficacy of these molecules as ultraviolet photoprotectors, even in strongly perturbing solvents. As such, we suggest these molecules might be well‐suited for augmentations to further im‐ prove their photoprotective efficacy or chemical compatibility with other components of sunscreen mixtures, whilst conserv‐ ing their underlying photodynamic properties.
A flow cytometry viability assay protocol is proposed and applied to model microalgae Chlorella vulgaris. The protocol relies on concomitant dual staining of the cells (fluorescein diacetate (FDA), propidium iodide (PI)) and machine learning processing of the results. Protocol development highlighted that working at 4 °C allows to preserve the stained sample for 15 min before analysis. Furthermore, the inclusion of an extracellular FDA washing step in the protocol improves the signal-to-noise ratio, allowing better detection of active cells. Once established, this protocol was validated against 7 test cases (controlled mixtures of active and non-viable cells). Its performances on the test cases are good: − 0.19%abs deviation on active cell quantification (processed by humans). Furthermore, a machine learning workflow, based on DBSCAN algorithm, was introduced. After a calibration procedure, the algorithm provided very satisfactorily results with − 0.10%abs deviation compared to human processing. This approach permitted to automate and speed up (15 folds) cytometry readings processing. Finally, the proposed workflow was used to assess Chlorella vulgaris cryostorage procedure efficiency. The impact of freezing protocol on cell viability was first investigated over 48-h storage (− 20 °C). Then, the most promising procedure (pelleted, − 20 °C) was tested over 1 month. The observed trends and values in viability loss correlate well with literature. This shows that flow cytometry is a valid tool to assess for microalgae cryopreservation protocol efficiency.