Avaliação do pré-tratamento ácido e hidrólise enzimática da palha de cana-de-açúcar para produção de etanol de segunda geração.

Abstract

Industrialization has consumed the relevance of knowledge about energy sources, currently consumption of fossil fuels represents 80% of world demand. Aiming at this problem arise the biofuels. Brazil is one of the largest biomass producers in the world. This biomass yields the Second Generation Ethanol (E2G). Biomass conversion involves pretreatment; hydrolysis; fermentation and the recovery of ethanol by distillation. Pretreatment is one of the bottlenecks in large-scale production. To evaluate the pre-treatment, an experimental design was used 22 plus three points, with the variables being studied the concentration of H3PO4 (0,5-2,5%, m / v) and time (10-30 minutes) plus three points, totaling 7 experiments. All pretreatment experiments were performed in an autoclave at a fixed temperature of 121 ° C, maintaining a solid: liquid ratio of 1:10. After the pre-treatments, the enzymatic hydrolysis (in duplicate) of the solid fractions obtained, under the following conditions: 50 ºC, pH 4,8 (sodium citrate buffer), under constant agitation of 150 rpm in shaker shaker, using An enzyme from the Cellulase Complex (Novozymes) was applied by applying an enzymatic charge of 15 FPU/gstraw for 72 hours. The pretreatment efficiency was evaluated by the release of reducing sugars obtained in the pretreatment, solubilization of the macromolecular components and concentration of reducing sugars in the enzymatic hydrolyzate. The results were analyzed through Statistica 10.0 software, at a significance level of 5% (α = 0.05). The pre-treatments presented a concentration of reducing sugars varying from 2,34 to 8,23 g / L. The highest macromolecular solubilizations, being 19,94 and 23,80%, respectively, for the most severe acid condition (2,5% m/v). The acid concentration and time employed were statistically significant for the solubilization of macromolecular components at 95% confidence. After analysis of variance (ANOVA) for the coded model of the first order, it was verified that it was significant. In relation to the release of reducing sugars after the step of enzymatic hydrolysis, the highest concentration reached 5,20 g / L, the pretreatment time of 30 minutes and the concentration of 2,5% (m/v) H3PO4, which refers to the more severe condition applied in the present study. In the range studied, the variables did not present statistical significance, but there was an indication of the influence of the acid concentration on the sugars released after the enzymatic hydrolysis. Lignin is a major drawback for dilute acid treatment, but the temperature and reaction time also interfere. It is necessary to re-evaluate the process conditions and to look for other hypotheses that can corroborate the viability of the production of 2G Ethanol.