Recovery and characterization of cellulosic ethanol from fermentation of sugarcane bagasse

Abstract

Industrial production of ethanol by fermentation using renewable feedstock such as sugarcane stalks has been demonstrated as a sustainable fuel chain in Brazil. This work focused on the production of cellulosic ethanol from sugarcane bagasse in a pilot scale unit by applying the current bioprocessing strategies with the aim of recovering and characterizing the end products. The feedstock was pretreated at 190 °C and a residence time of 10 min. Enzymatic hydrolysis was performed with commercial cellulolytic enzymes. Fermentation’s substrates were formulated with hydrolysate and supplemented with 8%wt sugarcane molasses. The fermentations were set up to mimic the conventional industrial fermentation in Brazil’s ethanol distilleries at high cell density with cell recycling. The fermentation resulted in a reproducible performance by the yield of 0.49 g/g, productivity of 6.96 g/(L∙h), and cell viability of 95.3%. Ethanol was recovered in a lab-scale distillation batch system. Distilled fractions showed higher content of higher alcohols and sulfur content than the standard specification of ANP (National Agency of Petroleum - Brazilian Agency) for ethanol fuel. The distillation bottom product (vinasse) presented most characteristics suitable for fertilizer or biogas applications, except for sodium and sulfate content. Therefore, for a successful technology, transference processing adjustments should be made to make the product commercially suitable and the side stream compatible for disposal as fertilizer or digestion for biogas production.