Bacteria Metabolism Reversed to Produce High-Speed Biofuel

Ramon Gonzalez (left) with student Clementina Dellomonaco (Jeff Fitlow/Rice University)

A new method developed by researchers at Rice University in Houston turns simple glucose into biofuels and petrochemical substitutes by reversing a metabolic process called beta oxidation using genetically modified bacteria. Engineering professor Ramon Gonzalez and colleagues published their findings online in the journal Nature (paid subscription required).

The beta oxidation process is a basic form of metabolism, carried out by species from single-celled bacteria to human beings that use it to break down fatty acids and generate energy. Gonzalez’s process reverses beta oxidation to produce butanol, a short-chain molecule, with a backbone of four carbon atoms. Most biotech researchers working on biofuels seek to use metabolic processes to build long-chain fatty acids, those with 10 carbon atoms or more.

The Rice team reversed the beta oxidation cycle by selectively manipulating about a dozen genes in the bacteria Escherichia coli (E. coli). The engineered E. coli then feed on a diet of inexpensive glucose and mineral salts to produce butanol. And, says Gonzalez, the E. coli produce butanol about 10 times faster than other organisms, as reported in scientific literature.

Butanol has a major advantage over many other biofuels, such as ethanol, in that it can substitute directly for gasoline in most vehicles, without any modifications to the engines. The industry calls these fuels “drop-in substitutes.”

The reverse beta-oxidation can produce other drop-in products besides butanol. Gonzalez and colleagues found they can manipulate bacterial genes to produce fatty acids of particular lengths, including long-chain molecules like those found in the chemicals stearic acid and palmitic acid, which have chains of more than a dozen carbon atoms.

“This is not a one-trick pony,” says Gonzalez. “We can make many kinds of specialized molecules for many different markets.”

Read more: E. Coli Engineered to Produce High-Volume Biofuel

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