SACARIFICACIÓN ENZIMÁTICA DE BAGAZO DE CAÑA DE AZÚCAR PRETRATADO CON PEROXIDO DE HIDROGENO PARA LA PRODUCCIÓN DE BIOETANOL

Abstract

<p><strong>Background.</strong> Sugarcane (<em>Saccharum officinarum</em> L.) is one of the main crops in Mexico; during the harvest 2021-2022, 54.6 million tons of raw milled sugarcane were industrialized, ranking sixth in production worldwide. However, during processing, several products and co-products are generated, including sugarcane bagasse, that is used to produce electricity by combustion, converting nearly 25% of its weight into greenhouse gases and generating environmental problems. For this reason, it is necessary to design processes aligned with the axes of sustainable development (environmental, social and economic) to promote valorization and diversification. <strong>Objective</strong>. To determine the effect of two pretreatments on the enzymatic saccharification of sugarcane bagasse for its subsequent conversion to bioethanol. <strong>Methodology.</strong> The production of enzymatic extracts by solid state fermentation (SSF) was carried out using sugarcane bagasse as support-substrate and autochthonous fungal strains as inoculum. For the enzymatic saccharification the sugarcane bagasse was pretreated with hydrogen peroxide and microwaves, for the hydrogen peroxide pretreatment the variables time (1, 3 and 6 h), ratio mL of peroxide per gram of bagasse (16. 6:1, 33.3:1 and 100:1), temperature (26, 50 and 70°C) and peroxide concentration (1, 3 and 5%); and for microwave pretreatment the variables microwave power (p30, p50 and p80) and time (5 and 10 min) were evaluated. For the enzymatic saccharification, enzymatic extracts produced by SSF and bagasse pretreated with hydrogen peroxide were used. Finally, fermentable sugars obtained from the enzymatic saccharification of sugarcane bagasse were used as a unique carbon source in alcoholic fermentation system. <strong>Results.</strong> The SSF results showed the presence of cellulase (2 U/g) and xylanase (61 U/g) activity. On the other hand, the results of pretreatment of sugarcane bagasse with hydrogen peroxide indicated that the best conditions were 100 mL of 3% hydrogen peroxide per gram of sugarcane bagasse at 50°C, while the best conditions of microwave pretreatment were 50p for 5 minutes. The enzymatic saccharification of sugarcane bagasse showed a maximum yield of reducing sugars when the sugarcane bagasse was pretreated with hydrogen peroxide, obtaining 0.41 g/g. Finally, the maximum ethanol concentration (4.32 g/L) was obtained after 48 hours of fermentation with commercial <em>Saccharomyces cerevisae</em>. <strong>Implications.</strong> The sugar agroindustry in Mexico is limited to the production of sucrose and ethanol, being necessary a sustainable productive diversification. <strong>Conclusions.</strong> The isolation of autochthonous fungal strains allowed the production of cellulases and xylanases by solid fermentation with adequate specificity to hydrolyze/saccharify pretreated sugarcane bagasse and its subsequent conversion to ethanol.</p>