US: Third gen aromatic biofuel breakthrough

The US Department of Energy Joint BioEnergy Institute (JBEI) and Lawrence Berkeley National Laboratory (Berkley Lab) have discovered an enzyme that enables the production of a renewable alternative to toluene, a petroleum-based octane booster in gasoline that sells 29 million tons per year.

According to the researchers, the enzyme enables the production of aromatic hydrocarbon biofuel from microbial activity for the first time. The scientists’ goal was to produce industrially and commercially viable fuels and chemicals from renewable sources. They studied two sources of toluene-producing microbes: lake sediment and sewage sludge.

A bacterium that produced toluene was identified in 1986, but the mechanisms behind it remained a mystery until the JBEI and Berkley Lab team revisited the discovery. Drawing from a community of microbes, rather than a single species, the new study identifies glycyl radical enzymes (GREs) as the genes responsible for producing the fuel.

“All enzyme discovery projects are challenging. But moving from discovery in a single bacterial species, to discovery in a complex microbial community from sewage sludge or lake sediments, was more difficult by orders of magnitude,” said Harry Beller, lead author of the study, Berkeley Lab senior scientist and scientific lead at JBEI. “This study became a needle-in-a-haystack search for the toluene-producing enzyme in a candidate pool of hundreds of thousands of enzymes.”

The team has high hopes for the enzyme, who say that it will enable the production of aromatic fuel hydrocarbon from renewable resources, as well as having implications for fundamental and applied science.

“We have so much to learn about the extraordinary metabolic diversity of bacteria,” Beller said. “Through eons of evolution, nature has devised enzymes that can catalyse difficult chemical reactions, and as we discover these, we can harness them for biotechnology.”

The paper is called ‘Discovery of enzymes for toluene synthesis from anoxic microbial communities’ and was published in Nature Chemical Biology 19 March.