Several research groups at universities and companies have been searching for ways to make renewable fuels that are similar enough to petroleum-based gasoline, diesel, and jet fuel to be used in existing vehicles. Such fuels would be more versatile than ethanol, which can't be used in high concentrations in ordinary engines. The LS9 discovery is a boost to this effort.

But work remains before the genes can make commercial quantities of fuel at prices that can compete with fossil fuels. "This is a long way from describing a commercially viable process for making alkanes," Arnold says. "Fuel has to be dirt cheap. It's not clear that we're ever going to make it cheap and easy by this route." One fundamental challenge is scaling up the process. "It all comes down to whether you can send enough carbon through that pathway to get to industrial levels," she says.

LS9 has been genetically engineering E. coli to optimize the process by which the bacteria converts sugar into fuel.For example, the E. coli naturally feeds on some of the fatty acids it produces, rather than using them as a feedstock for producing alkanes. LS9 is altering the bacteria so that they don't eat the fatty acids, which helps increase fuel yields, says Andreas Schirmer, LS9's associate director of metabolic engineering.

The company's first fuel to market will probably not be a hydrocarbon. Four years ago, the company began developing a fuel based on fatty esters that it says could serve as a replacement for diesel fuel, and is closer to market than the hydrocarbon fuel it started developing two years ago when it first identified the alkane genes and enzymes.