One-vessel saccharification and fermentation of pretreated sugarcane bagasse using a helical impeller bioreactor

The effect of Tween® 80 and the cellulase load, on the enzymatic hydrolysis of hydrothermally pretreated sugarcane bagasse (HPSB), was evaluated in shake flask experiments, using experimental design. The optimized conditions were further applied in a second set of shake flask experiments to study the effect of the biomass load. The overall optimum parameters, e.g., 6.9% Tween® 80, 15 FPU/g glucan, and 150 g/L (dry HPSB), were used in hydrolysis experiments carried out in a laboratory-scale bioreactor equipped with a helical impeller. After a 48 h reaction time, 60% of the HPSB glucan content was hydrolyzed into glucose. The same bioreactor and hydrolysis conditions were used for one-vessel saccharification and fermentation experiments as follows: 150 g/L (dry HPSB) was hydrolyzed at 50 °C and 150 rpm for either 24 or 48 h, followed by the bioreactor’s temperature and mixing decrease to 30 °C and 90 rpm for ethanol fermentation by Saccharomyces cerevisiae. Experiments resulted in ethanol yields of 48 or 52%, for hydrolysis time of 24 or 48 h, respectively, taking into account the HPSB glucan content. The best ethanol productivity, for the overall process of 0.51 g/L.h, was achieved for the 24 h hydrolysis time.