|CHAPLA, DIGANTKUMAR - Sardar Patel Renewable Energy Research Institute|
|PARIKH, BHUMIKA - Sardar Patel Renewable Energy Research Institute|
|KUMAR, ADEPU - Sardar Patel Renewable Energy Research Institute|
Submitted to: Journal of Biobased Materials and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/21/2014
Publication Date: 8/1/2015
Citation: Chapla, D., Parikh, B.S., Liu, L.Z., Cotta, M.A., Kumar, A.K. 2015. Enhanced cellulosic ethanol production from mild-alkali pretreated rice straw in SSF using Clavispora NRRL Y-50464. Journal of Biobased Materials and Bioenergy. 9(4):381-388(8).
Interpretive Summary: The high cost of cellulosic ethanol conversion, in large part from additional enzyme cost, poses a significant challenge to the sustainable production of advanced biofuels using lignocellulosic materials including agricultural residues. Conventional cellulosic ethanol production by simultaneous saccharification and fermentation (SSF) requires both cellulase and ß-glucosidase to decompose biomass polymers for microbial fermentation. Genetic engineering efforts have been made to enable ethanologenic organisms to produce ß-glucosidase in order to lower enzyme cost, however, the resulted strains’ performance were economically unsatisfactory. ARS recently developed a novel ethanol producing yeast strain Clavispora NRRL Y-50464 that is able to produce sufficient native ß-glucosidase enzyme activity. The efficacy of this strain was further demonstrated in a successful cellulosic ethanol SSF process from industrial processed corncobs waste. In the current research, scientists from ARS and India evaluated the potential of this strain for cellulosic ethanol production from mild alkaline pretreated rice straw. We found a relatively high level of ethanol production was achieved in 36h using strain Y-50464 without addition of external ß-glucosidase. These results suggest the new yeast strain has a great potential for lower-cost cellulosic ethanol production from rice straw. Findings of this research impact consolidated bioprocessing industrial development for sustainable advanced biofuels production.
Technical Abstract: This study reports the first lower-cost cellulosic ethanol production from mild alkali retreated rice straw using a native ß-glucosidase producing yeast strain, Clavispora NRRL Y-50464 by SSF. Ethanol production and efficiency of ethanol conversion from 10, 15, and 20% of solids loading of rice straw were investigated. Using 15% solids loading, an ethanol production of 25g/L was achieved at 36h incubation without supplementation of exogenous ß-glucosidase. A maximum ethanol production of 25.7 g/L was reached at 60h. Ethanol conversion efficiency (% theoretical yield) at this level was estimated at 50.5%. Y-50464 is an extremely fast growing yeast strain and completed its fermentation on 5% glucose in 18 h. The efficient cellulosic ethanol conversion from rice straw and short fermentation process time demonstrated in this study suggest a promising potential to utilize this new strain Clavispora NRRL Y-50464 for cost-efficient renewable biofuels production towards an economic consolidated bioprocessing industry.