Key Ethanol Tolerance Gene Identified in Biomass-Degrading Bacteria


If a single organism could breakdown cellulosic biomass and synthesize biofuels, a process known as consolidated bioprocessing, it could significantly increase the efficiency and reduce the costs of biofuel production. Some biomass-degrading microbes such as Clostridium thermocellum can also synthesize ethanol, but they are poisoned by relatively low ethanol concentrations compared to sugar fermenters such as yeast or E. coli. Researchers at the DOE Bioenergy Science Center (BESC) have now identified a key gene in C. thermocellum that is related to enhanced ethanol tolerance. The team analyzed genomes of C. thermocellum mutants that could tolerate higher than normal ethanol concentrations, and found a consistently modified gene involved in alcohol metabolism. By analyzing the structure of the encoded protein, it was determined that the mutation causes significant alterations to central ethanol metabolism. The identification of this gene will enable more targeted metabolic engineering approaches to improve production of ethanol and other biofuels in C. thermocellum and other biomass-degrading microbes useful for consolidated bioprocessing.


Brown, S. D., A. M. Guss, T. V. Karpinets, J. M. Parks, N. Smolin, S. Yang, M. L. Land, D. M. Klingeman, A. Bhandiwad, M. Rodriguez, Jr., B. Raman, X. Shao, J. R. Mielenz, J. C. Smith, M. Keller, and L. R. Lynd. 2011. “Mutant Alcohol Dehydrogenase Leads to Improved Ethanol Tolerance in Clostridium thermocellum,” Proceedings of the National Academy of Sciences of the United States of America 108, 13752-57. DOI:10.1073/pnas.1102444108.