ARS | Publication request: Hydrothermal pretreatment and enzymatic saccharification of corn stover for efficient ethanol production

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 16, 2012
Publication Date: November 16, 2012
Citation: Saha, B.C., Yoshida, T., Cotta, M.A., Sonomoto, K. 2013. Hydrothermal pretreatment and enzymatic saccharification of corn stover for efficient ethanol production. Industrial Crops and Products. 44:367-372.

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 necessary because corn stover in its native state is resistant to enzymatic hydrolysis. In this research, we evaluated liquid hot water pretreatment as an option for pretreatment of corn stover. We demonstrated that liquid hot water pretreatment 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: Corn stover used in this study contained 37.0±0.4% cellulose, 31.3±0.6% hemicellulose and 17.8±0.2% lignin on dry basis. Hydrothermal pretreatment and enzymatic saccharification were evaluated for conversion of corn stover cellulose and hemicellulose to fermentable sugars. Under the optimum conditions of hydrothermal pretreatment of corn stover (10%, w/v; 200oC; 5 min) and enzymatic saccharification (45oC, pH 5.0, 72 h), a total of 550±5 mg of fermentable sugars was obtained per g corn stover which is equivalent to 72% of theoretical sugar yield. The non-detoxified corn stover hydrolyzate was fermented by recombinant Escherichia coli strain FBR 5 at pH 6.5 and 37oC for 74 h to produce 20.9±0.5 g ethanol from 42.8±1.7 g sugars per L with a yield of 0.49 g ethanol per g available sugars and 0.27 g ethanol per g corn stover which is equivalent to 68.7% of theoretical ethanol yield from corn stover.