Sugarcane bagasse (SCB) is a lignocellulosic by-product of the production of (1G) ethanol and is a promising substrate for second generation (2G) bioethanol production. Since pretreatment of a lignocellulosic biomass is required to improve bioconversion (releasing fermentable sugars such as pentoses), it also produces a great amount of chemical of inhibitors of the subsequent fermentation. Although a number of technologies have been employed to remove fermentation inhibitors from lignocellulosic hydrolysate, they increase process costs. Scheffersomyces stipitis is able to utilize pentoses by the metabolic pathway and by laboratory evolution. Induced mutagenesis techniques, such as ultraviolet (UV) radiation and chemical compounds (EMS: ethyl methane sulfonate) have been shown to lead to a significant improvement in xylose utilization by yeast cells, and thus in ethanol fermentation yields. As a preliminary step, the present work aims to evaluate S. stipitis strains tolerance, growth and bioethanol production capacity at fed batch after two distinct lignocellulosic pretreatment methods applied (using sugarcane bagasse as substrate): acid catalysis and hydrothermal. Concomitantly, sequential mutagenesis using EMS and near and far UV radiations will be conducted to obtain S. stipitis strains with genetic variability and tolerant to the inhibitor compounds at the hydrolysate. To better investigate the mutant yeast, molecular characterization of the mutant will be performed, considering differences in the genetic profile. Furthermore, a bioethanol production system with high cells density of mutant S. stipitis obtained by cell recycling will be used to examine the characteristics of bioethanol (2G) fermentation using sugarcane bagasse hydrolysate as substrate (pretreatment method selected in the preliminary step).
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