ARS | Publication request: Cellulosic Ethanol Production from Xylose-extracted Corncob Residue by SSF Using Inhibitor- and Thermal-tolerant Yeast Clavispora NRRL Y-50339

Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 27, 2010
Publication Date: N/A

Technical Abstract: Xylose-extracted corncob residue, a byproduct of the xylose-producing industry using corncobs, is an abundant potential energy resource for cellulosic ethanol production. Simultaneous saccharification and fermentation (SSF) is considered an ideal one-step process for conversion of lignocellulosic biomass to ethanol applying enzymatic hydrolysis of the biomass and concurrent fermentation of released sugars by yeast. However, due to inhibitory compounds generated during economic dilute acid pretreatment and different temperature requirements for optimized enzyme hydrolysis and microbial fermentation, SSF of cellulosic ethanol conversion is often performed far less efficiently. We report a thermal-tolerant yeast strain of Clavispora NRRL Y-50339 that is tolerant to common inhibitors derived from lignocellulose deconstruction, such as furfural and 5-hydroxymethylfurfural, in application for a simple and low-cost cellulosic ethanol production by SSF using post xylose extracted corncob residues. Since this strain is able to produce beta-glucosidase, a commonly required second enzyme for cellobiose digestion involved in complete cellulosic degradation, no additional beta-glucosidase needs to be added when utilizing Y-50339 for SSF. Using non-detoxified slurry (25% WIS) of dilute acid pretreated corncob residues (neutralized at pH 5.5) as the sole carbon source and a crude cellulase enzyme for primary cellulose digestion, we obtained a cellulosic ethanol conversion yield at 204 g/kg of available corncob cellulose with an ethanol concentration of 23 g/L in 120 h at 37 deg C by triplicate 2-L bioreactor experiments. This study provides potential efficient means for lower-cost cellulosic ethanol production using an industrial byproduct of corncob residues and other lignocellulosic biomass.