Efficient bioethanol production from sodium hydroxide pretreated corn stover and rice straw in the context of on-site cellulase production

A novel and efficient bioprocess from sodium hydroxide pretreated corn stover (SHPCS) or sodium hydroxide pretreated rice straw (SHPRS) to ethanol was successfully established, where the on-site cellulase production by the mixed culture of Trichoderma reesei and Aspergillus niger was used, producing 3.63 ± 0.35 FPIU/mL cellulase from SHPCS and 2.56 ± 0.33 FPIU/mL cellulase from SHPRS, respectively. Then those cellulases were applied to the enzymatic saccharification of SHPCS and SHPRS respectively, leading to yields of 81.5 ± 1.2% and 70.5 ± 2.1% respectively. Subsequently, SHPCS and SHPRS enzymatic hydrolysates mainly containing glucose and xylose were fermented by Saccharomyces cerevisiae, producing 27.6 ± 1.5 and 21.7 ± 1.9 g/L ethanol respectively. Concurrent with the distillation of fermentation broths for ethanol separation, the residual xylose was concentrated about 3 times. Thereafter, the distillation residues from SHPCS and SHPRS containing xylose were fermented by the adapted Pichia stipistis, producing 16.6 ± 1.1 and 13.0 ± 0.9 g/L ethanol respectively. In sum, the bioprocess could produce 33.1 g ethanol from 113.20 g SHPCS and 26.0 g ethanol from 117.58 g SHPRS.