Concerns about long-term fossil fuel availability, coupled with environmental problems resulting from their production and use, have spurred increased efforts to synthesize biofuels from renewable resources.

A new strategy has been developed by UCLA professor of chemical and biomolecular engineering James Liao, postdoctoral fellow Shota Atsumi and visiting professor Taizo Hanai.

"These alcohols are typically trace byproducts in fermentation," Liao said. "To modify an organism to produce these compounds usually results in toxicity in the cell. We bypassed this difficulty by leveraging the native metabolic networks in E. coli but altered its intracellular chemistry using genetic engineering to produce these alcohols."

The research team modified key pathways in E. coli to produce several higher-chain alcohols from glucose, a renewable carbon source, including isobutanol, 1-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol and 2-phenylethanol.

This strategy leverages the E. coli host's highly active amino acid biosynthetic pathway by shifting part of it to alcohol production. In particular, the research team achieved high-yield, high-specificity production of isobutanol from glucose.

This new strategy opens an unexplored frontier for biofuels production, both in coli and in other microorganisms.

"The ability to make these branched-chain higher alcohols so efficiently is surprising," Liao said. "Unlike ethanol, organisms are not used to producing these unusual alcohols, and there is no advantage for them to do so. The fact that they can be made by E. coli is even more surprising, since E. coli is not a promising host to tolerate alcohols. These results mean that these unusual alcohols in fact can be manufactured as efficiently as what evolved in nature for ethanol. Therefore, we now can explore these unusual alcohols as biofuels and are not bound by what nature has given us."