Gut Microbe Makes Diesel Biofuel

Reconfiguring the genetics of the food pathogen E. coli produces hydrocarbons indistinguishable from those burned in trucks

By David Biello

E. coli can now replicate the hydrocarbon molecules that burn predominantly in big trucks and other powerful moving machines. Image: Flickr/Carlos de Paz

Welding bits and pieces from various microbes and the camphor tree into the genetic code of Escherichia coli has allowed scientists to convince the stomach bug to produce hydrocarbons, rather than sickness or more E. coli. The gut microbe can now replicate the molecules, more commonly known as diesel, that burn predominantly in big trucks and other powerful moving machines.

"We wanted to make biofuels that could be used directly with existing engines to completely replace fossil fuels," explains biologist John Love of the University of Exeter in England, who led the research into fuels. "Our next step will be to try to develop a bacterium that could be deployed industrially." Love?s work was published April 22 in Proceedings of the National Academy of Sciences.

That means harnessing E. coli's already high tolerance for harsh conditions, such as the high acidity and warmth of the human digestive tract. That hardiness also seems to be helping the bacterium survive its own production of such longer-chain hydrocarbons, which could have proved toxic to the microbes, in the way brewer's yeast cells are killed off by the alcohol they ferment. The engineered E. coli used genetic code from the insect pathogen Photorhabdus luminescens and from the cyanobacterium Nostoc punctiforme as well as its fellow gut microbe Bacillus subtilis to make the fuel molecules from fatty acids, along with a gene from the camphor tree?Cinamomum camphora?to cut the resulting hydrocarbon to the right length.

The E. coli are currently fed on sugar and yeast extract, which suggests that the resulting fuel would be expensive compared with the kind refined from oil found in the ground. "We are hopeful that we could change their diet to something less valuable to humanity," Love suggests. "For example, organic wastes from agriculture or even sewage."

Exactly how the E. coli microbes expel the diesel fuel molecules is unknown at this point. The researchers have found them floating in the growth medium, suggesting the microbes are somehow secreting the hydrocarbons from their cells once produced. "We don't know how they get there yet," Love admits. But that may solve a problem posed to other would-be biofuels produced in microbes; algal oils have proved difficult to extract cheaply and effectively from inside the algae themselves, among other challenges.

Source: http://rss.sciam.com/click.phdo?i=d7ead1449b1788bf22e13a011d3ffafa

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