Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/18/2013
Publication Date: 5/21/2013
Citation: Saha, B.C., Cotta, M.A. 2013. Biological pretreatment of corn stover by Phlebia brevispora for enhanced enzymatic hydrolysis and efficient ethanol production [abstract]. American Society for Microbiology. Poster No. 2475.
Technical Abstract: Pretreatment, as the first step towards conversion of lignocellulosic feedstocks to ethanol remains one of the main barriers to commercial success. Typically, harsh methods are used to pretreat lignocellulosic biomass prior to its breakdown to sugars by enzymes, which also result in fermentation inhibitor formation. An alternative to harsh chemicals is biological pretreatment to break down or remove lignin from the holocellulose surface. After screening 26 white rot fungal strains using corn stover for powerful ability to remove lignin from it with minimum loss of cellulose and hemicellulose, we have selected Phlebia brevispora for further investigation. Pretreatment of corn stover by P. brevispora using solid state fermentation under three different conditions (moisture content, inoculum size and duration) was investigated. Changes in composition of pretreated corn stover and its susceptibility to enzymatic hydrolysis were analyzed. Growth of the fungus was estimated by measuring ergosterol content of the pretreated corn stover. Enzymatic hydrolysis of pretreated corn stover was performed using commercial cellulase, ß-glucosidase and hemicellulase preparations. Ethanol production of P. brevispora pretreated corn stover by fed-batch simultaneous saccharification and fermentation (SSF) was investigated using Saccharomyces cerevisiae D5A, xylose utilizing recombinant S. cerevisiae YRH400 and mixed sugar utilizing ethanologenic recombinant Escherichia coli FBR5. About 84% moisture and 42 days incubation at 28 oC were found to be optimal for pretreatment with respect to enzymatic saccharification. Inoculum size was not important. Ergosterol data shows continued growth of the fungus studied up to 57 days. No fermentation inhibitors were produced. The sugar yield was 442±5 mg/g of pretreated corn stover. About 36±0.6 g ethanol was produced from 150 g pretreated stover per L by fed-batch SSF using the recombinant E. coli strain. The ethanol yields were 32.0±0.2 and 38.0±0.2 g from 200 g pretreated corn stover per L by fed-batch SSF using S. cerevisiae D5A and recombinant yeast strain, respectively. This research demonstrates that biological pretreatment with P. brevispora has high potential to be used for lignocellulosic biomass pretreatment.