Comparison of SHF and SSF processes for ethanol production from alkali-acid pretreated sugarcane trash

Abstract

Sugarcane trash, an agricultural by-product, contained 16.21% neutral detergent soluble (NDS), 38.43% hemicellulose, 34.06% cellulose, 5.51% lignin and 5.79% ash on dry solid (DS) basis. After it was pretreated with 2%w/v NaOH followed by 2%w/v H2SO4 in autoclave (121oC, 15 min), the content of cellulose, hemicellulose and lignin were 73.17%, 7.21% and 3.41%, respectively. The pretreated sugarcane trash was used as substrate for ethanol production in separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) processes, using commercial cellulase and Saccharomyces cerevisiae TISTR 5596 cells. The optimum conditions in a flask scale of SHF process (15% w/v substrate loading hydrolyzed with cellulase 50 FPU/g DS at 50oC, pH 5.0 and fermentation at 30oC), and SSF process (20%w/v substrate loading, cellulase 50 FPU/g DS, hydrolysis and fermentation at 35oC,pH 5.0) were applied to compare the ethanol production in a fermenter. In the SSF process, the highest level of ethanol production was 57.75 g/L, which was 16.26% higher than that of SHF process (48.36 g/L). The SSF process was therefore provided a more efficient method for the utilization of sugarcane trash.