Comparison of process configurations for ethanol production from acid- and alkali-pretreated corncob by Saccharomyces cerevisiae strains with and without β-glucosidase expression

β-Glucosidase was shown to have synergistic effects with commercial cellulase in the hydrolysis of acid- and alkali-pretreated corncob, especially at the dose of 5 U/g biomass and 5 or 10 FPU/g biomass. An integrating yeast strain 45# expressing β-glucosidase was constructed that utilized cellobiose quickly and efficiently. Process configurations were compared under conditions of 10% solid content, 10 FPU cellulase/g biomass, 5 U β-glucosidase/g biomass (only used for parental strain W303-1A), 1 g/kg yeast loading and 3.3 g/kg urea supplementation. While separate hydrolysis and fermentation was optimal for W303-1A and the ethanol titer and yield reached 3.22 g/100 g and 75.6% (expressed as a percentage of the theoretical yield), respectively, simultaneous saccharification and fermentation was optimal for strain 45# and the ethanol titer and yield reached 3.31 g/100 g and 77.7%, respectively. These results are valuable in optimization of the process configuration and improving the yeast strain selected for cellulosic ethanol production.