Submitted to: Industrial Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2013
Publication Date: 2/20/2014
Citation: Saha, B.C., Cotta, M.A. 2014. Alkaline peroxide pretreatment of corn stover for enzymatic saccharification and ethanol production. Industrial Biotechnology. 10(1):34-41.
Interpretive Summary: Corn stover can 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 an alkali based pretreatment method. The pretreated corn stover has been used for ethanol production by both separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). The SSF offers advantage for process simplication and total time required for conversion of corn stover to ethanol. This research is important for development of an integrated commercially viable biomass to ethanol conversion process technology.
Technical Abstract: Alkaline hydrogen peroxide (AHP) pretreatment and enzymatic saccharification were evaluated for conversion of corn stover cellulose and hemicellulose to fermentable sugars. Corn stover used in this study contained 37.0±0.2% cellulose, 26.8±0.2% hemicellulose and 18.0±0.1% lignin on dry basis. Under the optimum conditions of AHP pretreatment [2% H2O2 (v/v), pH 11.5, 35oC, 24 h] of corn stover (10%, w/v) and enzymatic saccharification (45oC, pH 5.0, 72 h) with 0.1% (w/v) Tween 20, a total of 558±7 mg of fermentable sugars was obtained per g stover which is equivalent to 79.5% of theoretical sugar yield. Most of the lignin (82%) was removed from corn stover. The AHP pretreated and enzymatically saccharified corn stover hydrolyzate was fermented by recombinant Escherichia coli strain FBR 5 at pH 6.5 and 37oC for 96 h to produce 23.9±0.9 g ethanol from 56.6±1.6 g total sugars per L with an ethanol yield of 0.42 g/g available sugars and 0.24 g/g corn stover which is equivalent to 67% of theoretical ethanol yield from corn stover. The strain produced 25.0±0.3 g ethanol per L in 120 h from AHP pretreated corn stover (10%, w/v) by simultaneous saccharification and fermentation at pH 6.0 and 37oC with a yield of 0.25 g/g stover. This is the first report on the production of ethanol from AHP pretreated corn stover by a recombinant bacterium.