Alexis Spalletta

Les molécules amphiphiles, entités capables de modifier la tension superficielle entre deux surfaces, peuvent être obtenues par différentes méthodes dont la principale est synthétique, à partir de substrats pétrosourcés. Leur omniprésence dans de multiples domaines a créé un marché mondial et, par conséquent, des attentes écologiques et économiques envers leur production. Il est donc nécessaire de trouver de nouvelles voies de conception écoresponsables et biosourcées. Les processus biocatalysés, impliquant notamment des enzymes, peuvent répondre à cet objectif. À titre d'exemple, les esters glucidiques d'acides gras sont des tensioactifs biosourcés qui peuvent être synthétisés par des lipases. Cependant, beaucoup de paramètres peuvent influencer ces synthèses.Notre premier objectif a été d’étudier l’impact du milieu réactionnel et des substrats sur la synthèse d’un ester glucidique d'acide gras, le 6-O-lauroyl-D-glucopyranose, par une lipase, et notamment l’influence d’un agent solubilisant, permettant de moduler la solubilité initiale des substrats, sur l’efficacité et la sélectivité de la réaction.Un espaceur peut être ajouté au tensioactif afin d’améliorer ses propriétés ou de lui en conférer une ou plusieurs supplémentaires. L’objectif a donc par la suite été de concevoir un synthon lipophile-espaceur, le lauryl(3-hydroxypropyl)succinate, en deux étapes. Dans la première, un alcool gras, le dodécan-1-ol, a été condensé sur de l'acide succinique en utilisant une lipase comme biocatalyseur. Selon des paramètres de référence préalablement mis au point, plusieurs lipases ont été considérées pour conduire au monolauryl succinate et au dilauryl succinate. Ensuite, le propan-1,3-diol est ajouté au milieu réactionnel pour réagir avec les produits de la première étape et conduire au lauryl(3-hydroxypropyl)succinate. Nous avons, pour chaque lipase utilisée, cartographié différents paramètres du milieu réactionnel comme le solvant, le co-solvant, la quantité d’eau ajouté, ou encore l’effet de l’empreinte moléculaire. Nous pouvons ainsi proposer une synthèse multi-étapes optimisée et plus sélective du lauryl(3-hydroxypropyl)succinate en 4 h, sans traitement ni purification intermédiaire entre les étapes. Enfin, le greffage du lauryl(3-hydroxypropyl)succinate sur un D-glucose a été mis en place à l'aide d'une β-glucosidase, afin d’obtenir le tensioactif. Sur la base des résultats obtenus, ce projet a pour perspective la modification de la tête polaire au profit de sucres aux propriétés spécifiques et intrinsèques, comme le D-Allose, ainsi que de l’espaceur et de l’alcool.

The emergence of resistant bacterial and fungal strains poses significant challenges in various industrial processes including food, medicines, and leather industry. It necessitates the development of novel and effective antimicrobial agents. In the present work, we have developed an ecofriendly and sustainable approach to synthesize silver-doped copper oxide nanoparticles by using cinnamon bark extract (C-CuO/Ag). The nanoparticles were characterized via UV–visible spectroscopy at 190–800 nm, FT-IR, SEM-EDAX, XRD, and further subjected to determine antimicrobial potential, minimum inhibitory concentration (MIC), and anti-biofilm potential against both bacterial and fungal species. UV–visible spectrum showed maximum absorption at 210 nm in ultraviolet range and 419 nm in visible range. Various strong and weak peaks were obtained in FT-IR spectra, which defined the presence of corresponding functional groups in C–CuO/Ag nanoparticles. SEM analysis revealed the tightly packed confirmation, while EDS confirmed the elemental analysis of C-CuO/Ag nanoparticles. XRD spectrum of C-CuO/Ag nanoparticles showed strong diffraction peaks at 2Ө of 31.92˚, 35.67˚, and 48.51˚, which confined with the plane indices of (-110), (111), and (− 202), respectively, while weak diffraction peaks at 2Ө of 56.31˚, 58.9˚, and 77.4˚, which leads to the crystal planes of (202), (− 220), and (311), respectively. Antimicrobial assays showed clear zones of inhibition against microbial strains as maximum inhibition diameter was observed against Aspergillus niger (31.5 ± 0.7 mm) followed by Escherichia coli (30.1 ± 0.3 mm) and Staphylococcus aureus (29.5 ± 0.7 mm). These findings provide support clear evidence that CuO nanoparticles can serve as potent antibacterial and antifungal compounds against highly resistive and pathogenic microbial strains.

The present work focuses on the utilization of potato peel waste for the production of bioethanol. In the present study, extensive screening was undertaken to isolate amylolytic and cellulolytic microbes using starchy biomass. After confirming the chemical composition of potato peel waste (PPW), several trials were performed to enhance the amylase and cellulase production from Bacillus subtilis to hydrolyze the PPW in submerged fermentation. Optimization of physical parameters was performed using both commercial and indigenous media from enzymatically hydrolyzed PPW. Different routes of various combinations were designed to enhance bioethanol production. The maximum ethanol titer of 0.50% and 0.41% was recorded in Route B and A, i.e., separate saccharification and ethanol fermentation and consolidated fermentation. Simultaneous saccharification and fermentation (SSF) also measured a good ethanol yield of 0.46%. The fermented residual cake was checked for nutritional components and showed a high content of protein and amino acids because of the addition of unicellular yeasts. This cake can be utilized as an animal feed supplement.

Carbohydrate-based surfactants are amphiphilic compounds containing hydrophilic moieties linked to hydrophobic aglycones. More specifically, carbohydrate esters are biosourced and biocompatible surfactants derived from inexpensive renewable raw materials (sugars and fatty acids). Their unique properties allow them to be used in various areas, such as the cosmetic, food, and medicine industries. These multi-applications have created a worldwide market for biobased surfactants and consequently expectations for their production. Biobased surfactants can be obtained from various processes, such as chemical synthesis or microorganism culture and surfactant purification. In accordance with the need for more sustainable and greener processes, the synthesis of these molecules by enzymatic pathways is an opportunity. This work presents a state-of-the-art lipase action mode, with a focus on the active sites of these proteins, and then on four essential parameters for optimizing the reaction: type of lipase, reaction medium, temperature, and ratio of substrates. Finally, this review discusses the latest trends and recent developments, showing the unlimited potential for optimization of such enzymatic syntheses.

Surfactants are amphiphilic molecules with the ability to modify the surface tension between two surfaces. They can be obtained by various methods, the main one being synthetic, from petroleum-based substrates. Their universal use in a wide range of fields has created a global market and, consequently, ecological, and economic expectations for their production. Biocatalyzed processes, involving enzymes, can address this objective with processes complying with the principles of green chemistry: energy saving, product selectivity, monodispersity, and reduction in the use of solvents, with energy eco-efficiency. For example, fatty-acid carbohydrate esters are biobased surfactants that can be synthesized by lipases. In this work, we were interested in the synthesis of D-glucose lauric ester, which presents interesting properties described in the literature, with Aspergillus niger lipase, rarely described with sugar substrates. We optimized the synthesis for different parameters and reaction media. This lipase appeared to be highly selective for 6-O-lauroyl-D-glucopyranose. However, the addition of DMSO (dimethyl sulfoxide) as a co-solvent displays a duality, increasing yields but leading to a loss of selectivity. In addition, DMSO generates more complex and energy-intensive purification and processing steps. Consequently, a bio-sourced alternative as co-solvent with 2MeTHF3one (2-methyltetrahydrofuran-3-one) is proposed to replace DMSO widely described in the literature.