Simultaneous saccharification and fermentation process of different cellulosic substrates using a recombinant Saccharomyces cerevisiae harbouring the β-glucosidase gene

Abstract

In Brazil, the production of ethanol from sugarcane produces large amounts of lignocellulosic residues (bagasse and straw), which have been driving research and development for the production of second generation ethanol. In the present work, a recombinant Saccharomyces cerevisiae strain expressing the β-glucosidase gene from Humicola grisea was used for ethanol production from three different cellulosic sources by simultaneous saccharification and fermentation. Initially, a enzymatic pre-hydrolysis step was done with a solid:liquid ratio of 1:4, and an enzymatic load of 25 filter paper activity (FPU).g^-1 of cellulosic substrate. Using sugarcane bagasse pretreated cellulignin, crystalline cellulose and carboxymethyl cellulose, 51.7 g L^-1, 41.7 g L^-1 and 13.8 g L^-1 of ethanol was obtained, respectively, at the end of 55 hrs of fermentation. The highest ethanol productivity (0.94 g L^-1 hrs^-1) was achieved using sugarcane bagasse pretreated cellulignin. The use of a recombinant S. cerevisiae led to extremely low glucose concentrations when compared to other works reported in literature.