Location: Bioenergy Research Unit
Title: Fuel ethanol production from alkaline peroxide pretreated corn stover Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 17, 2014
Publication Date: May 20, 2014
Citation: Saha, B.C., Cotta, M.A. 2014. Fuel ethanol production from alkaline peroxide pretreated corn stover [abstract]. American Society for Microbiology. Poster No. 2250. Technical Abstract: Corn stover (CS) has the potential to serve as an abundant low-cost feedstock for production of fuel ethanol. Due to heterogeneous complexity and recalcitrance of lignocellulosic feedstocks, pretreatment is required to break the lignin seal and/or disrupt the structure of crystalline cellulose to increase the accessibility of cellulolytic enzymes. Alkaline peroxide pretreatment (AHP) is known to delignify agricultural residues, with concomitant increase in saccharification efficiency. Milled CS (10%, w/v) was slurried in water containing 2% (v/v) H2O2 and adjusted to pH 11.5 using 10 M NaOH and shaken in an incubator at 250 rpm at 35 oC for 24 h, unless otherwise specified. The enzymatic hydrolysis of the AHP pretreated CS was performed by shaking slowly (100 rpm) at 45 oC for 72 h after diluting the pretreated material to 5% solids level (unless otherwise specified), adjusting the pH to 5.0 with conc. HCl and adding a filter sterilized enzyme cocktail of 3 commercial enzyme preparations. Ethanol production of AHP pretreated CS by separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) was investigated under semi-anaerobic conditions using a mixed sugar utilizing ethanologenic recombinant Escherichia coli FBR5. CS 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, 35 oC, 24 h] of CS (10%, w/v) and enzymatic saccharification (45 oC, pH 5.0, 72 h) with 0.1% (w/v) Tween 20, a total of 557±12 mg of fermentable sugars was obtained per g CS which is equivalent to 79.5% of theoretical sugar yield. Most of the lignin (82%) was removed from CS. The AHP pretreated and enzymatically saccharified CS hydrolyzate was fermented by E. coli FBR 5 at pH 6.5 and 37 oC 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 CS. The strain produced 25.0±0.3 g ethanol per L in 120 h from AHP pretreated CS (10%, w/v) by SSF at pH 6.0 and 37 oC with a yield of 0.25 g/g stover. This research demonstrates that AHP is an effective pretreatment option for conversion of CS to fuel ethanol.