Use of Lignocellulosic Biomass: Pretreatment and Fermentation for the Production of Bioethanol

The growing demand for renewable resources has promoted research oriented towards bioethanol production. In this study, different pretreatments of lignocellulosic biomass were evaluated, specifically sugarcane bagasse, coffee husks, and rice husks, using two different alkaline, alkaline-peroxide processes. The experimental conditions consisted of pH 11.5 and incubation at 35 °C for 24 h. The leachates were analyzed to determine the total sugar content, which was used as an indirect indicator of the efficiency of each pretreatment. On the basis of the results, the alkaline-peroxide pretreatment was selected as the most efficient. Subsequently, pretreated wastes were subjected to dilute acid hydrolysis in a ratio of 1:30 (w/v) with 1 % (v/v) sulfuric acid and autoclaved at 120 °C for 1 h. In the fermentation stage, a 32 factorial design with two replicates was applied, evaluating combinations of temperatures of 30 °C, 35 °C and 40 °C and pH values of 4, 5 and 7. A concentration of 5 % (v/v) of yeast Saccharomyces cerevisiae was kept constant. The optimal conditions found were 35 °C and pH 4 and the yield in bioethanol production varied significantly between the waste evaluated, rice husks showed the lowest yield (6.848 g/L), while sugarcane bagasse and coffee husks achieved a production of 24.196 and 14.728 g/L, respectively.