Improved cellulosic ethanol production from corn stover with a low cellulase input using a ß-glucosidase-producing yeast following a dry biorefining process

Authors: GEBEREKIDAN, MESFIN - East China University Of Science And Technology; ZHANG, JIAN - East China University Of Science And Technology; Liu, Zonglin; BAO, JIE - East China University Of Science And Technology

Submitted to: Bioprocess and Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2018
Publication Date: 11/8/2018
Citation: Geberekidan, M., Zhang, J., Liu, Z.L., Bao, J. 2018. Improved cellulosic ethanol production from corn stover with a low cellulase input using a ß-glucosidase producing yeast. Bioprocess and Biosystems Engineering. 42(2): 297-304. https://doi.org/10.1007/s00449-018-2034-9.
DOI: https://doi.org/10.1007/s00449-018-2034-9

Interpretive Summary: Current cellulosic ethanol conversion from lignocellulosic materials requires significant extra expenses of hydrolytic enzymes to release fermentable sugars for microbial utilization. Reducing the expense on the digestive enzyme is vital for a sustainable and efficient cellulosic ethanol production from lignocellulosic biomass. ARS scientist developed a new yeast strain Clavispora NRRL Y-50464 that is able to produce beta-glucosidase and produce cellulosic ethanol from corn stover. However, the conventional bioreactor designed for traditional liquid fermentation is not suitable for cellulosic ethanol production using simultaneous saccharification and fermentation (SSF) process. In this research, ARS scientist collaborated with scientists at East China University of Science and Technology and significantly increased the efficiency of cellulosic ethanol production from corn stover through a processing engineering approach. They applied a special designed bioreactor with a helical stirring apparatus that provided sufficient mixing power and mass transferring capability during enzymatic hydrolysis for higher levels of cellulosic ethanol production. It significantly reduced the cost of enzyme needed for SSF and the ethanol yield reached near the minimum industrial production standard. Outcomes of this study impact renewable bioenergy community in both academic and industrial sectors. This collaborative research provides a reference and guidelines for continued improvement of low-cost cellulosic ethanol production from lignocellulosic materials.

Technical Abstract: A low-cost and sustainable cellulosic ethanol production is vital for fermentation based industrial applications. Reducing the expenses of cellulose-deconstruction enzymes is one of significant challenges for economic cellulose-to-ethanol conversion. Here we report the improved ethanol production from corn stover using a natural ß-glucosidase producing strain Clavispora NRRL Y-50464 with a low cellulase dose of 5 mg protein/g cellulose under separate enzymatic hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) conditions. Strain Clavispora NRRL Y-50464 exhibited a superior ethanol fermentation performance over Saccharomyces cerevisiae DQ1 under both conditions. It produced an ethanol titer of 38.1 g/L at a conversion efficiency of 55.5% with 25% solids loading (w/w) via SSF without addition of extra ß-glucosidase supplement. Results of this study suggested strain Y-50464 has a potential as a candidate for lower-cost cellulosic ethanol production from lignocellulosic materials.