Isomérisation et hydrogénation des huiles végétales pour la production des acides linoléiques conjugués

Ce travail doctoral présente différentes voies de recherches pour l'élaboration d'un catalyseur hétérogène bifonctionnel favorisant la production des acides linoléiques conjugués (ALC) bénéfiques pour la santé humaine, aux dépens des acides gras trans (AG/) et saturés (AGs) néfastes, au cours du procédé d'hydrogénation/isomérisation de l'huile de carthame. De tous les catalyseurs à base de cristallites de métaux très dispersées sur la silice mesoporeuse SBA-15, modifiée ou non avec l'aluminium, qui ont été synthétisés et testés pour l'hydrogénation/isomérisation de l'huile de carthame, le catalyseur 1%Rh/SBA-15 s'avère être le plus actif et optimise la production des ALC sous des conditions opératoires douces de transfert de matière gaz/liquide/solide. L'huile partiellement hydrogénée contient 73 mg ALC/g huile et moins de 2% AGt mono-insaturés. L'addition de 1 ppm de soufre permet de doubler la production à 131 mg ALC/g huile avec 8% AGr mono-insaturés. Un mécanisme réactionnel est proposé pour décrire les effets positifs du soufre sur l'activité d'isomérisation de conjugaison de 1%Rh/SBA-15

Physical and Enzymatic Hydrolysis Modifications of Potato Starch Granules

In this work, a valorization of the starch stemming from downgraded potatoes was approached through the preparation of starch nanoparticles using different physical methods, namely liquid and supercritical carbon dioxide, high energy ball milling (HEBM), and ultrasonication on the one hand and enzymatic hydrolysis on the other hand. Starch nanoparticles are beneficial as a reinforcement in food packaging technology as they enhance the mechanical and water vapor resistance of polymers. Also, starch nanoparticles are appropriate for medical applications as carriers for the delivery of bioactive or therapeutic agents. The obtained materials were characterized using X-ray diffraction as well as scanning and transmission electron microscopies (SEM and TEM), whereas the hydrolysates were analyzed using size exclusion chromatography coupled with pulsed amperometric detection (SEC-PAD). The acquired results revealed that the physical modification methods led to moderate alterations of the potato starch granules’ size and crystallinity. However, enzymatic hydrolysis conducted using Pullulanase enzyme followed by nanoprecipitation of the hydrolysates allowed us to obtain very tiny starch nanoparticles sized between 20 and 50 nm, much smaller than the native starch granules, which have an average size of 10 μm. The effects of enzyme concentration, temperature, and reaction medium pH on the extent of hydrolysis in terms of the polymer carbohydrates’ fractions were investigated. The most promising results were obtained with a Pullulanase enzyme concentration of 160 npun/g of starch, at a temperature of 60 °C in a pH 4 phosphate buffer solution resulting in the production of hydrolysates containing starch polymers with low molecular weights corresponding mainly to P-10, P-5, and fractions with molecular weights lower than P-5 Pullulan standards

Laccase-Mediated Grafting of Phenolic Compounds onto Lignocellulosic Flax Nanofibers

Lignocellulosic nanofibres (LCNF) are nanometer additives that can be used to improve the mechanical, esthetical, optical and thermal properties of polymers in composites, packages, or coatings. Surface modification of these hydrophilic nanometer additives is needed to improve their properties and applicability in hydrophobic polymers matrix. In this work, two phenolic monomers, guaiacol and syringaldehyde were for the first time, efficiently grafted onto the exposed residual lignin of lignocellulosic nanofibres surface by a laccase from Trametes versicolor mediated reaction. Guaiacol grafted (LCNFG) and syringaldehyde grafted (LCNFS) lignocellulosic nanofibres were characterized with Fourier Transform Infra-Red (FTIR) and UV–visible techniques. Thermal and hydrophobic properties were analyzed by thermogravimetric analysis (TGA) and Water contact angle (WCA) measurements. FTIR analyzes confirmed the laccase mediated grafting of guaiacol and syringaldehyde onto lignocellulosic nanofibres. UV–visible gave evidence for the grafting of phenolic entities onto lignocellulosic nanofibres by factual data supporting experimental observations, leading to brown and orange colored grafted lignocellulosic nanofibres (LCNFG and LCNFS, respectively). TGA has shown that grafting of phenolic compounds endowed LCNF better thermal stability. WCA angle and wettability measurements showed that the surface hydrophobicity of LCNFG and LCNFS was increased after the enzymatic grafting modification