Monday, April 30, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Dilute acid pretreatment is a promising pretreatment technology for conversion of lignocellulosic biomass to fuel ethanol. Corn stover (supplied by a local farmer) used in this study contained 37.0±0.4% cellulose, 31.3±0.6% hemicelluloses, and 17.8±0.2% lignin. 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. We have optimized dilute sulfuric acid (0.0-1.0%, v/v; 140-200oC; 5-15 min) pretreatment and enzymatic saccharification (pH 5.0, 45oC, 72 h) of corn stover (10%, w/v) using commercial cellulase and β-glucosidase preparations. No hemicellulase was needed. The optimal conditions for dilute acid pretreatment were: 0.75% H2SO4, 160oC, and 5 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 optimized cellulase (15 FPU/g glucan) and β-glucosidase (12 U/g glucan) doses generated 66.0±3.5 g total sugars per 100 g of stover which is equivalent to 87.8% of the theoretical sugar yield based on the total carbohydrate content of the stover. In addition, it produced 0.86 g furfural per 100 g of corn stover. However, 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 separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) will be presented.