EFFECTS OF THE INCREASE IN SUBSTRATE LOAD AND HYDROLYSIS TIME IN THE SACCHARIFICATION OF SUGARCANE BAGASSE AND ETHANOL PRODUCTION

Abstract

In this study, the enzymatic saccharification of alkaline pretreated sugarcane bagasse (PSB) and the production of second generation bioethanol were investigated under different conditions. The effects of percentage of dry substrate (3 and 10% w/v) and time of hydrolysis (24 and 72 h) were evaluated in order to obtain maximum contents of total reducing sugar (TRS), glucose and xylose. The monosaccharide concentrations were quantified by High Performance Liquid Chromatography (HPLC) and TRS by the 3.5-dinitrosalicylic acid (DNS) method. The saccharification of PSB with the Cellic Ctec3, promoted an efficient release of sugars. Among the four evaluated conditions, the hydrolysis HD (10% PSB and 72h) was selected as the most efficient with the highest concentrations of released sugars: TRS (73.96 g/L), glucose (31.78 g/L) and xylose (10.85 g/L). The alcoholic fermentation of hydrolysate HD with the yeast Saccharomyces cerevisiae produced the maximum concentration of 16.15 g/L of ethanol, with a volumetric productivity (QP) of 0.69 g/Lh and yield of ethanol as a function of the substrate (YP/S) of 0.48 gethanol/gsugar. S. cerevisiae was capable of fermenting 99.96% of glucose from hydrolysate HD. These results suggest that the increase of the substrate load and time in the enzymatic hydrolysis can be favourable alternatives to improve the sugar yields in hydrolysates and, consequently, the bioethanol production.