The Integrated Process of Microbial Ensiling and Hot-Washing Pretreatment of Dry Corn Stover for Ethanol Production

In this study, we used dry corn stover (DCS) silage as feedstock to produce ethanol using hot-washing treatment (HWT) followed by prehydrolysis and fed-batch simultaneous saccharification and fermentation (FD-SSF) using cellulase and Saccharomyces cerevisiae. The inoculants product for ensiling of DCS was composed of lactic acid-producing organisms, such as Lactobacillus casei, Lactobacillus fermentum and Enterococcus durans. Moreover, the appropriate condition was selected by the dynamic analysis of silage quality. Among test conditions, the pH value (4.22), pretreatment time (4 week) and the content of lactic acid in DCS silage (4.32%) could be considered as important indicators of the success of microbial ensiling. The 16S rRNA gene-based pyrosequencing was used to analyze the community of the resulting silage, and the results indicated that Lactobacillus was the advantageous species. The observed glass transition temperature (Tg) value for DCS silage occurred at a temperature of 124.2 °C (Tmid). DCS silage was hydrothermally treated at temperature of Tg for 20 min. It was proved that biomass can be pretreated for cellulosic ethanol production by the integrated process of microbial ensiling and HWT. Ethanol fermentation of HWT-treated (at 30% glucan loading) DCS silage hydrolyzate (resulting in 61.92 g/L ethanol at 59.15% metabolic yield of FD-SSF) was reported in this work.