Second-generation ethanol production by separate hydrolysis and fermentation from sugarcane bagasse with cellulose hydrolysis using a customized enzyme cocktail

Abstract

Lignocellulosic materials are a valuable energy source that can be used to reduce dependence on fossil fuels. However, the high cost of enzymes and low efficiency of enzymatic hydrolysis are among the main bottlenecks regarding production of bioethanol. The purpose of the current work is to present the full use of sugarcane bagasse in the production of biofuels: as a carbon source for the production of competitive enzymes and as a platform for conversion of the cellulose and hemicellulose fractions into ethanol. Hydrolysis of pretreated sugarcane bagasse, using an enzymatic cocktail from naturally occurring microorganisms, was carried out, producing cellulose hydrolysate. This hydrolysate was further fermented to ethanol, achieving a concentration of 33 g/L, which corresponded to a fermentation efficiency of 89% and a high volumetric productivity of 11 g/(L·h). From the hemicellulose fraction, 18 g/L of ethanol was produced, which corresponds to a fermentation efficiency of 87%. Hence, from both cellulose and hemicellulose fractions, the overall ethanol concentration was 6.5% (v/v). These results indicate that production of ethanol through separate hydrolysis and fermentation (SHF) is a promising strategy, since it makes it possible to achieve high productivities during fermentation. Also, the possibility of converting xylose to ethanol can lead to an increase in production.