Location: Bioenergy Research Unit
Title: A new yeast producing beta-glucosidase and tolerant to lignocellulose hydrolysate inhibitors for cellulosic ethanol production using SSF Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 5, 2011
Publication Date: May 5, 2011
Citation: Liu, Z., Cotta, M.A., Weber, S.A. 2011. A new yeast producing beta-glucosidase and tolerant to lignocellulose hydrolysate inhibitors for cellulosic ethanol production using SSF [abstract]. In: Proceedings of the 33rd Symposium on Biotechnology for Fuels and Chemicals, May 2-5, 2011, Seattle, Washington. Paper No. 12-04. Technical Abstract: Conventional cellulose-to-ethanol conversion requires cellulose degradation in order to be utilized for growth and fermentation by common ethanologenic yeast. Cellulose is commonly enzymatically degraded into cellobiose by cellulase and subsequently cellobiose broken down into glucose by beta-glucosidase. Thus, both cellulase and beta-glucosidase enzymes are required for a complete cellulose hydrolysis in a simultaneous saccharification and fermentation (SSF). In addition, due to a higher temperature required for an optimal enzyme hydrolysis and a lower temperature for the yeast fermentation, temperatures have to be compromised in SSF. This not only complicates the fermentation procedures but also increases the cost significantly. In this study, we report a new yeast that is able to produce beta-glucosidase and ethanol from cellulose so no additional beta-glucosidase needs to be added into the SSF reaction procedure. Through evolutionary engineering efforts, we further improved the yeast for tolerance to higher temperatures and inhibitors associated with lignocellulose hydrolysate such as furfural and hydroxymethylfurfural (HMF). Using the newly designed yeast, an ethanol yield of 23 g/L was obtained with a 25% solid load of xylose-extracted corncobs at 37 deg C by SSF without the addition of beta-glucosidase. The yeast showed strong tolerance and in situ detoxification capabilities of furfural and HMF. Its fast growth rate and inhibitor detoxification of the fermentation medium exceeded Saccharomyces cerevisiae. The SSF was completed in five days without application of beta-glucosidase compared with S. cerevisiae in seven days with the addition of the enzyme. The new yeast has a potential for lower-cost cellulosic ethanol production.