reported a different course. In a recent issue of the journal Nature, the team led by James Liao, described how they genetically modified a well-known bacterium, Escherichia coli, to efficiently synthesize butanol, a molecule it doesn’t normally produce.
To do this, the team reasoned that they could divert some of the metabolites that E. coli uses to make amino acids, the building blocks of proteins, to a metabolic pathway that would result in the production of butanol. “Amino acid biosynthesis is very well studied in E. coli,” Liao explains. Using that knowledge, Liao’s team inserted two genes into the E. coli genome: one from a microbe involved in the production of cheese and one from a yeast. These genes express proteins that convert keto acids, components of the amino acid biosynthesis pathway, into butanol. In addition, by inhibiting the expression of other genes and making changes in certain proteins in the pathway, Liao was able to increase the efficiency of the process to a level high enough for industrial use. “By using these two tricks we could force the flux to the desired direction,” he says. “We were able to produce isobutanol very quickly and improved the titer in a few months.”
The technology is so promising that Gevo Inc., a biofuels startup based in Pasadena, Calif., recently announced that it acquired an exclusive license to commercialize Liao’s process. The company is currently scaling up the technology and deciding whether to go ahead with its own plans to build a butanol plant.
Liao, meanwhile, is working on converting cellulose waste materials into isobutanol as well as trying to implement the approach in other microbes. “We’re very excited about the promise of the project,” he says.
Jessica Ebert is a Biomass Magazine staff writer.