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Etude de la bioconversion de la chènevotte (cannabis sativa) et de l’alfa (stipa tenacissima) par prétraitement thermomécanique en présence d’un catalyseur acide ou alcalin

Abstract : In a context of an awareness of energy consumption and environmental preservation, this thesis aims to respond through the study of a process of bioethanol fuel production from lignocellulosic biomass (LCB). LCB, which is an important source of cellulose, is a hydrolyzable polymer by enzymatic action and provides monomer sugars fermentable into ethanol. The complex and recalcitrant structure of the lignocellulosic matrix (cellulose, hemicellulose, lignin) is a major obstacle to enzymatic attack and requires a pretreatment step to disrupt the physico-chemical barriers facing the accessibility of enzymes to the cellulosic polymers. The study of a hydrothermomechanical pretreatment combined with acid or alkali catalyst in low concentrations was carried out on two materials: hemp hurds (by-product of industrial hemp) and alfa (endemic plant in Morocco). The characterization of the two substrates showed the interesting potential in holocellulose for the bioconversion process and the analysis of pretreatment step results showed significant changes in the internal structure (FTIR, DRX), morphology (MEB), adsorption properties (BET) and chemical composition compared to the native raw materials. Increasing the specific surface area allowed improved hydrolysis yields due to better accessibility of enzymes to cellulosic polymers. From an environmental point of view, impregnation by spraying, by limiting the generation of residual liquid fractions, is more advantageous than impregnating by immersion. Hemp hurds, with its hardwood structure, showed a neutralizing capacity and required more quantities of acid catalyst compared to alfa. The experimental design aimed for the determination of pretreatment optimal conditions that maximize sugar yield and was carried out in both acid and alkali conditions. This method was also used for studying and optimisation of enzymatic hydrolysis conditions. Sugar yields of 90 and 83.2% for sulphuric acid pretreatment and sodium hydroxide were respectively achieved. Fermentation tests of the glucose enriched hydrolysate produced yields of 54.1 and 46.4% in ethanol.
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Imane Semhaoui. Etude de la bioconversion de la chènevotte (cannabis sativa) et de l’alfa (stipa tenacissima) par prétraitement thermomécanique en présence d’un catalyseur acide ou alcalin. Autre. Université de La Rochelle; Université Sidi Mohamed ben Abdellah (Fès, Maroc), 2019. Français. ⟨NNT : 2019LAROS018⟩. ⟨tel-02517352⟩

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