LS9's process is built on E. coli bacteria's metabolic machinery for converting sugars into fatty acids, which they then use to make other molecules. The advantage of working with E. coli is that the organism, a workhorse of molecular biology, is well known and easy to grow, says Keasling. And the bacterium's fatty acid pathway is more efficient at turning feedstocks into fuel than metabolic pathways used by other synthetic biology companies.

Fatty acids are a large class of molecules that can form the basis of many commodity chemicals and fuels that are conventionally derived from petroleum. These metabolic pathways are complex networks, and taking advantage of them required changing several of the bacterium's existing genes as well as adding new ones. After years of engineering, says Keasling, "we can get the molecule we want specifically."

Del Cardayre says LS9 has tested the diesel-production process at its 1,000-liter pilot-scale plant in South San Francisco using sugarcane as a feedstock. The company will scale the process to a commercial level at a 75,000-liter plant this year.

LS9 isn't the only company turning sugarcane into diesel: last year, another synthetic biology company founded by Keasling, Amyris Biotechnologies of Emeryville, CA, opened a demonstration plant in Campinis, Brazil. Amyris's process is based around yeast engineered to convert sugars into hydrocarbon-fuel precursors. Del Cardayre says LS9 may open a plant in Brazil as well, but because the new bacteria can convert cellulose, not just sugar, the company isn't tied to sugarcane or any other feedstock.

Jim Collins, professor of biomedical engineering at Boston University, says the question now is whether LS9's process will be cost-effective on a large scale. "As you go from 10 gallons to thousands of gallons, the biology changes, and analyses that worked well in the lab no longer work," notes Collins, because the microbes' environment changes. "The interesting question in the next few years is, which company can get their yields high enough, and get their processes up to scale to keep costs down," says Collins.