Biological pretreatment of corn stover with Phlebia brevispora NRRL-13108 for enhanced enzymatic hydrolysis and efficient ethanol production

Authors: Saha, Badal; Kennedy, Gregory - Greg; Qureshi, Nasib; Cotta, Michael

Submitted to: Biotechnology Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2016
Publication Date: 1/28/2017
Publication URL: https://handle.nal.usda.gov/10113/5801863
Citation: Saha, B.C., Kennedy, G.J., Qureshi, N., Cotta, M.A. 2017. Biological pretreatment of corn stover with Phlebia brevispora NRRL-13108 for enhanced enzymatic hydrolysis and efficient ethanol production. Biotechnology Progress. 33(2):365-374.

Interpretive Summary: Biological pretreatment of lignocellulosic biomass by white-rot fungus can represent a low-cost and eco-friendly alternative to harsh physical or chemical pretreatment methods to facilitate enzymatic hydrolysis. However, fungal pretreatment can cause carbohydrate loss and it is therefore necessary to use the appropriate fungal strain-biomass type combination. In this work, solid state cultivation of a selected fungal strain was optimized for fermentable sugar production from corn stover after enzymatic hydrolysis. Ethanol can be produced efficiently from the pretreated corn stover by simultaneous saccharification and fermentation by a bacterium and yeast. The research demonstrates that this fungal pretreatment can be used to improve the enzymatic hydrolysis of corn stover and efficient production of fuel ethanol.

Technical Abstract: Biological pretreatment of lignocellulosic biomass by white-rot fungus can represent a low-cost and eco-friendly alternative to harsh physical, chemical, or physico-chemical pretreatment methods to facilitate enzymatic hydrolysis. In this work, solid state cultivation of corn stover with Phlebia brevispora NRRL-13018 was optimized with respect to duration, moisture content, and inoculum size. Changes in composition of pretreated corn stover and its susceptibility to enzymatic hydrolysis were analyzed. About 84% moisture and 42 days incubation at 28 degrees Celsius were found to be optimal for pretreatment with respect to enzymatic saccharification. The inoculum size tested was not important. Ergosterol data shows continued growth of the fungus studied up to 57 days. No furfural and hydroxymethyl furfural were produced. The total 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 simultaneous saccharification and fermentation (SSF) using mixed sugar utilizing ethanologenic recombinant E. coli FBR5 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 xylose utilizing recombinant S. cerevisiae YRH400 strain, respectively. This research demonstrates that P. brevispora NRRL-13018 has potential to be used for biological pretreatment of lignocellulosic biomass.