Cellulase Recycling Via Vacuum Distillation During Cellulosic Ethanol Production

High cellulase cost is the main obstacle for commercialization of cellulosic ethanol production. Cellulase recycling is the most efficient method to reduce enzyme cost and ethanol production cost. However, the current reported cellulase recycling methods were related to high enzyme dosage, low solids loading, pure cellulose etc, which were not feasible in practice. In this study, cellulase recycling via vacuum distillation was used during cellulosic ethanol production from delignified corncob residue and pretreated and biodetoxified corn stover. Ethanol was pumped out at lower temperature under vacuum condition, and cellulase activity remained at a high level. Following the first vacuum distillation operation, fresh material was fed into the bioreactor, and the next SSF operation was initiated. This repeated SSF process was conducted for 5 times with the delignified corncob residue and 3 times with the pretreated and biodetoxified corn stover. Meanwhile, enzyme activities against feedstock, pNPG, CMC were measured during the repeated SSF. Energy consumption was calculated through flowsheet simulation model established using Aspen plus software for comparison of ethanol production cost.20-44% enzyme dosage was saved and 14-27% ethanol production cost was decreased using repeated SSF. Considering the high price of cellulase, recycling via vacuum distillation is a promising strategy.In addition, delignified corncob residue (DCCR) was used as the feedstock of ethanol production by simultaneous saccharification and fermentation (SSF). The ethanol titer and yield reached 75.07 g/L and 89.38%, respectively, using a regular industrial yeast strain at moderate cellulase dosage and high solids loading. The fermentation performance and cost of DCCR and corn meal was compared as feedstock of ethanol fermentation. The result shows that the DCCR is competitive to corn meal as ethanol production feedstock.