Simultaneous saccharification and co-fermentation of corn stover pretreated by H2O2 oxidative degradation for ethanol production

Abstract

The simultaneous saccharification and co-fermentation of Saccharomyces cerevisiae and Candida tropicalis for ethanol production using H2O2-pretreated corn stover (CS) were performed in 250-mL or 500-mL Erlenmeyer flasks at various S. cerevisiae-C. tropicalis ratios (4:1, 3:1, 2:1, 1:1, 1:2, 1:3 and 1:4), fermentation temperatures (32 °C, 35 °C and 38 °C), inoculation ratios (8%, 12% and 16%), initial pH values (4.5, 5 and 5.5) and fermentation times (96 h, 120 h and 144 h). The optimum S. cerevisiae-C. tropicalis ratio derived from mono-factor design test was 3:1. According to orthogonal design experiment results, the optimum fermentation temperature, inoculation ratio, initial pH and fermentation time with a dry solid substrate content of 25% were 32 °C 12%, 5.0 and 144 h, respectively, and the maximum ethanol concentration was 10.924 g/100 mL. The cell growth, ethanol production and total substrate consumption in the process of simultaneous saccharification and co-fermentation conformed to logistical model, Luedeking-Piret model and general substrate consumption law of mono-strain fermentation, respectively. Collectively, S. cerevisiae and C. tropicalis simultaneously produced ethanol from xylose and glucose without interference, respectively.