Pré-tratamentos organossolve e hidrotérmico do bagaço e palha de cana-de-açúcar e hidrólise enzimática do licor hemicelulósico visando a produção de bioetanol

Abstract

The demand for the development of technologies to produce biofuels is intended to present a sustainable alternative compared to fossil fuels, providing a reduction in the emission of pollutants, and promoting the use of clean and renewable energy sources. With this, we have the production of second-generation ethanol (2G ethanol), which is a biofuel obtained through fermentation processes of sugars from lignocellulosic biomass, which can therefore be obtained using agro-industry residues as raw material. To optimize the production of bioethanol, it is necessary to carry out an effective and economical pre-treatment of the lignocellulosic biomass to make the polysaccharides more accessible to enzymatic hydrolysis. Among the existing pretreatments, we can highlight organosolv and hydrothermal. which, applied to the biomass, result in the separation of the cellulose pulp (solid fraction) and the liquor rich in hemicelluloses and lignin (liquid fraction). This study aimed to evaluate the efficiency of the organosolv and hydrothermal pre-treatments of sugarcane bagasse and straw and to obtain the hemicellulosic liquor. After analysis and characterization of the raw and pre-treated biomass, an increase in the proportion of cellulose in relation to the lignin and hemicellulose content was demonstrated, indicating that the delignification occurred effectively. The hemicellulose liquors resulting from the pretreatments were subjected to lignin precipitation to obtain a liquor rich in hemicelluloses for the enzymatic hydrolysis step with the commercial cocktail Cellic CTec3. Then, the liqueurs were characterized before and after the enzymatic hydrolysis regarding the total reducing sugars (ART) content, in which an increase in the ART concentration of the organosolv sugar cane bagasse liqueurs was verified (11.144 ± 0.530 to 13.440 ± 0.081 g.L-1), hydrothermal bagasse (16.507 ± 1.679 to 22.492 ± 0.074 g.L-1), organosolv sugarcane straw (8.560 ± 0.237 to 9.478 ± 0.687 g.L-1) and hydrothermal sugarcane straw (14,164 ± 0.478 to 22.830 ± 0.781 g.L-1). In addition, the data were compared by high performance liquid chromatography (HPLC), which, despite the formation of inhibitory compounds, also showed an increase in the concentration of sugars, mainly xylose. So, we have that the use of hemicellulosic liquor has potential for application in fermentation processes with specific yeasts for pentoses resulting in the production of bioethanol and thus, adding value to agro-industrial residues applied to a context of a biorefinery.