High-Temperature Microbe Metabolically Engineered to Produce Biofuel Alcohols
The U.S. bioethanol industry depends largely on glucose conversion by yeast wherein pyruvate is decarboxylated to acetaldehyde and then reduced to the 2-carbon biofuel, ethanol. Interest is growing, however, in microorganisms that produce longer-chain alcohols with superior characteristics as fuel molecules compared to ethanol. Examples include microbial strains engineered to produce a specific alcohol such as isopropanol, n-butanol, or isopentanol. Much of the research to date focuses on engineered organisms that operate at ambient temperatures (e.g, 37°C), but the ability to produce bioalcohols at temperatures above 70°C has several advantages over ambient-temperature processes, including lower risk of microbial contamination, higher diffusion rates, and lower cooling and distillation costs. Researchers at the Department of Energy’s BioEnergy Science Center describe the metabolic engineering of a hyperthermophilic archaeon, Pyrococcus furiosus, to produce not only ethanol but a range of alcohols at 70-80°C via a synthetic pathway not known in nature and fundamentally different from those previously described. Specifically, the researchers engineered P. furiosus to produce various alcohols from their corresponding organic acids by constructing a novel synthetic route termed the aldehyde ferredoxin oxidoreductase (AOR)/alcohol dehydrogenase (AdhA) pathway. For example, in addition to converting acetate to ethanol, the synthetic pathway was shown to convert longer chain acids such as propionate to propanol, isobutyrate to isobutanol, and phenylacetate to phenylalcohol. This study is the first example of significant alcohol formation in an archaeon, emphasizing the biotechnological potential of novel microorganisms for biofuel production.
Basen, M., G. J. Schut, D. M. Nguyen, G. L. Lipscomb, R. A. Benn, C. J. Prybol, B. J. Vaccaro, F. L. Poole, R. M. Kelly, and M. W. W. Adams. 2014. “Single Gene Insertion Drives Bioalcohol Production by a Thermophilic Archaeon,” Proceedings of the National Academy of Sciences (USA) 111(49), 17,618-623. DOI: 10.1073/pnas.1413789111.