ARS | Publication request: Fuel ethanol production from corn stover under optimized dilute phosphoric acid pretreatment and enzymatic hydrolysis

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 16, 2012
Publication Date: June 19, 2012
Citation: Avci, A., Saha, B.C. 2012. Fuel ethanol production from corn stover under optimized dilute phosphoric acid pretreatment and enzymatic hydrolysis [abstract]. American Society for Microbiology General Meeting. Poster No. 351.

Technical Abstract: Ethanol is a renewable oxygenated fuel. Dilute acid pretreatment is a promising pretreatment technology for conversion of lignocellulosic biomass to fuel ethanol. Generation of fermentable sugars from corn stover involves pretreatment and enzymatic saccharification. Pretreatment is crucial as native corn stover is very resistant to enzymatic hydrolysis. Dilute phosphoric acid (0.0-2.0%, v/v; 140-200oC; 5-25 min) pretreatment and enzymatic saccharification (pH 5.0, 45oC, 72 h) of corn stover (10%, w/v) using commercial cellulase, ß-glucosidase, and hemicellulase enzyme preparations were optimized. A mixed sugar utilizing ethanologenic recombinant Escherichia coli strain FBR5 was used to ferment the generated sugars by both separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). Corn stover used in this study contained 37.0±0.4% cellulose, 31.3±0.6% hemicelluloses, and 17.8±0.2% lignin. The optimal conditions for dilute phosphoric acid pretreatment were: 0.75% H3PO4, 160oC, and 15 min. The conditions were chosen based on maximum glucose release, minimum loss of pentose sugars, and minimum formation of sugar degradation products such as furfural and hydroxymethyl furfural (HMF). The pretreated corn stover after enzymatic saccharification using commercial cellulose, ß-glucosidase and xylanase preparations generated 57.7±0.4 g total sugars per 100 g of stover which is 76.4% of the theoretical sugar yield based on the total carbohydrate content of the stover. The pretreatment generated only 0.22±0.03 g furfural per 100 g of corn stover. No HMF was produced. The fermentative performance of the mixed sugar utilizing ethanologenic recombinant Escherichia coli strain FBR5 on the non-detoxified corn stover hydrolyzate by both SHF and SSF will be presented. This research demonstrates that dilute phosphoric acid pretreatment is a viable option to generate fermentable sugars from corn stover upon enzymatic hydrolysis and the recombinant E. coli strain FBR5 ferments the sugars efficiently.