The biofuel production technique consolidated bioprocessing (CBP) uses a microorganism’s own enzymes to liberate plant sugars and ferment them into ethanol, rather than adding an externally produced enzyme. To improve the ethanol tolerance of the microorganisms and encourage them to make more ethanol, the genetic basis behind CBP needs to be understood.

Steven Brown and colleagues, Oak Ridge National Laboratory, Tennessee, USA, have identified a single gene that controls ethanol production capacity in the microorganism Clostridium thermocellum. Resequencing of the genome of an ethanol-tolerant mutant of this organism showed that the tolerant phenotype is primarily due to a mutated bifunctional acetaldehyde-CoA/alcohol dehydrogenase gene.

The team hopes this information will allow evolution of a yet more tolerant strain that is capable of making higher concentrations of ethanol, which would lower biofuel production costs.

• Mutant alcohol dehydrogenase leads to improved ethanol tolerance in Clostridium thermocellum
  S. D. Brown, A. M. Guss, T. V. Karpinets, J. M. Parks, N. Smolina et al.
  Proc. Natl. Acad. Sci. 2011, 108(33), 13752—13757.
  DOI: 10.1073/pnas.1102444108