Location: Bioenergy Research Unit
Title: Response surface optimization of corn stover pretreatment using dilute phosphoric acid for enzymatic hydrolysis and ethanol production Authors
Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 14, 2012
Publication Date: December 22, 2012
Citation: Avci, A., Saha, B.C., Dien, B.S., Kennedy, G.J., Cotta, M.A. 2013. Response surface optimization of corn stover pretreatment using dilute phosphoric acid for enzymatic hydrolysis and ethanol production. Bioresource Technology. 130:603-612. Interpretive Summary: Corn stover contains 68% carbohydrates that could potentially be used for production of fuel ethanol. Generally, three steps are involved for its conversion to ethanol: pretreatment, enzymatic hydrolysis, and fermentation. Pretreatment is crucial because corn stover in its native state is resistant to enzymatic hydrolysis. In this research, we have optimized dilute phosphoric acid pretreatment for enzymatic hydrolysis and ethanol production from corn stover. We demonstrated that dilute phosphoric acid at high temperature is highly effective for generating sugars from corn stover. The corn stover hydrolyzate after enzymatic hydrolysis is readily fermentable to ethanol without removing fermentation inhibitors formed during pretreatment. These findings are important for development of a commercially viable biomass to ethanol conversion process technology.
Technical Abstract: Dilute H3PO4 (0.0 - 2.0%, v/v) was used to pretreat corn stover (10%, w/w) for conversion to ethanol. Pretreatment conditions were optimized for temperature, acid loading, and time using a central composite design. Optimal pretreatment conditions were chosen to promote sugar yields following enzymatic digestion while minimizing formation of furans, which are potent inhibitors of fermentation. The maximum glucose yield (85%) was obtained after enzymatic hydrolysis of corn stover pretreated with 0.5% (v/v) acid at 180 °C for 15 min while highest yield for xylose (91.4%) was observed from corn stover pretreated with 1% (v/v) acid at 160 °C for 10 min. About 26.4±0.1 g ethanol was produced per L by recombinant Escherichia coli strain FBR5 from 55.1± 1.0 g sugars generated from enzymatically hydrolyzed corn stover (10%,w/w) pretreated under a balanced optimized condition (161.81 ºC, 0.78% acid, 9.78 min) where only 0.4±0.0 g furfural and 0.1±0.0 hydroxyl methyl furfural were produced.