1-61: Comparison of continuous SSCF and batch SSCF processes for conversion of AFEX treated corn stover to ethanol using commercial enzymes and Saccharomyces cerevisiae 424A (LNH-ST)

Separate hydrolysis and co-fermentation (SHcF) of various AFEX treated biomass using commercial enzymes and Saccharomyces cerevisiae 424A (LNH-ST) have showed high sugar conversions and high ethanol yields without washing, detoxification and nutrients supplementation. Such achievements are attributed to the preserved nutrients, high digestibility and high fermentability of AFEX treated biomass. However, SHcF has not been able to meet the industrial requirements for cost effectiveness due to low productivity, as xylose fermentation is slow and incomplete. Simultaneous saccharification and co-fermentation (SSCF) combining enzymatic hydrolysis and fermentation can potentially reduce cost, improve productivity as well as enhance sugar conversion. If SSCF is performed in a continuous fashion, the reaction volume can be further reduced and productivity can be further enhanced. In the present study, both batch and continuous (CSTR) SSCF were performed on AFEX treated corn stover in fermentors. Sugar conversion, viable cells, ethanol production as well as monomeric and oligomeric sugar profiles were characterized. Two dilution rates were attempted to increase the rate of xylose fermentation in this continuous SSCF process. Mass balance for each process was also performed to facilitate comparison of each approach.