Lower-cost cellulosic ethanol production from corn stover using β-glucosidase producing yeast Clavispora NRRL Y-50464

For cellulosic ethanol production, decomposition of cellulosic polymers and enzymatic hydrolysis and saccharification are necessary for microbes to efficiently utilize the biomass harbored sugars.  The need of additional enzymes and processing steps increase the cost of biofuels.   Reducing the cost of cellulosic ethanol production is a critical challenge for sustainable and renewable advanced biofuels production.  Previously, we reported on a novel yeast Clavispora sp. NRRL Y-50464 that is able to utilize cellobiose as sole carbon source and produce sufficient native β-glucosidase enzyme activity for cellulosic ethanol production.   One of the enzymatic proteins was characterized and designated as BGL1, β-glucosidase from Clavispora strain Y-50464.  In this study, we report a lower-cost cellulosic ethanol production from corn stover using this yeast strain by simultaneous saccharification and fermentation.  Using replicated 2-L bioreactors, an ethanol production of 32g/L was obtained from 20% solids loading of undelignated cellulose, at 48 h applying cellulase alone but without addition of β-glucosidase.  Ethanol production reached 35g/L at 120h.  The post-fermentation residual cellulose was analyzed and an approximate 90% of efficiency of cellulose utilization was realized.  Elimination of exogenous β-glucosidase in cellulose-to-ethanol fermentation would be expected to reduce cost and improve efficiency of cellulose conversion.  Results of this study showed promising potential of this new yeast strain for sustainable cellulosic ethanol production.