Scarry science? E. Coli, the source of the ‘next biofuel’
January 23, 2008
Scientists have genetically engineered E. coli that is highly efficient in producing butanol, a new type of biofuel. This new technology could speed up the development of butanol biofuels into a cost-effective alternative to ethanol.
“It [butanol] has many attractive properties,” says Jim McMillan, manager of biorefining process R&D at the National Renewable Energy Laboratory’s National Bioenergy Center, in Golden, CO. Because butanol packs more energy per gallon than ethanol does, cars running on butanol get better mileage. And, unlike ethanol, it doesn’t mix with water, so it can be shipped in existing petroleum pipelines without causing problems.
Several research groups are engineering microbes that can convert sugar from various feedstocks into butanol. Most of these groups rely on the bacterium Clostridium acetobutylicum, which naturally makes a form of butanol called 1-butanol. However, this bacterium grows slowly and is not easy to genetically manipulate.
James Liao, a chemical engineer at the University of California, and his colleagues are looking into using E. coli. Although the bacterium does not produce butanol naturally, it is easy to modify and grows fast. Liao says that he can program E. coli to produce small amounts of butanol by diverting some of the microorganism’s metabolites into alcohol production. With further genetic modifications, Liao was able to dramatically increase the efficiency of the process. With further manipulation, the engineered microbes achieved efficiency high enough for industrial use.
To make butanol from keto acids, the researchers inserted two different nonnative genes into E. coli. The first gene came from a microbe commonly used in the production of cheese. The gene codes for an enzyme that converts keto acids into aldehydes. The second gene, derived from yeast, codes for an enzyme that converts aldehydes into butanol.
Gevo, a biofuels startup based in Pasadena, CA, has acquired an exclusive license to commercialise Liao’s technology.
Gevo isn’t alone in its pursuit of a better butanol-producing bug. In June 2006, BP and DuPont joined efforts to develop butanol.
Last June, BP and DuPont, along with Associated British Foods, announced their plans to build a biobutanol pilot plant at an existing BP site in England. The plant, which will use sugar beet as a feedstock, is expected to begin operations in 2009, with the ultimate goal of commercializing butanol after 2010.