Researchers at the Korea Advanced Institute of Science and Technology (KAIST) say they have developed, for the first time, a new method for microbial gasoline production through metabolic engineering of E. coli. They published their work (“Microbial Production of Short-Chain Alkanes”) online in Nature on September 29.

“Although microbial production of diesel has been reported, production of another much-in-demand transport fuel, petrol (gasoline), has not yet been demonstrated,” they wrote. “Here we report the development of platform Escherichia coli strains that are capable of producing short-chain alkanes (SCAs; petrol), free fatty acids (FFAs), fatty esters, and fatty alcohols through the fatty acyl (acyl carrier protein (ACP)) to fatty acid to fatty acyl-CoA pathway.”

Gasoline is a mixture of hydrocarbons, additives, and blending agents. The hydrocarbons (alkanes) consist only of carbon and hydrogen atoms. Gasoline has a combination of straight-chain and branched-chain alkanes consisted of 4–12 carbon atoms linked by direct carbon-carbon bonds.

Previously, through metabolic engineering of E. coli, there have been a few research results on the production of long-chain alkanes, which consist of 13–17 carbon atoms, suitable for replacing diesel. However, there has been no report on the microbial production of short-chain alkanes, a possible substitute for gasoline—until now.

The research team engineered the fatty acid metabolism to provide the fatty acid derivatives that are shorter than normal intracellular fatty acid metabolites, and introduced a novel synthetic pathway for the biosynthesis of short-chain alkanes. This allowed the development of a platform E. coli strain capable of producing gasoline for the first time. Furthermore, this platform strain, if desired, can be modified to produce other products such as short-chain fatty esters and short-chain fatty alcohols.

“It is only the beginning of the work toward sustainable production of gasoline,” said Sang Yup Lee, Ph.D., team leader in the department of chemical and biomolecular engineering. “The titer is rather low [580 mg of gasoline per liter of cultured broth] due to the low metabolic flux toward the formation of short-chain fatty acids and their derivatives. We are currently working on increasing the titer, yield, and productivity of bio-gasoline.”

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