E. Coli Gene-Tweaked to Make 5 - 8 Carbon Alcohols With Much Higher Energy Density Than Ethanol, Even Higher than Butanol

With alcohol fuels, the longer the carbon chain, the higher the energy density -- the more energy per gallon of fuel. Scientists at UCLA have tweaked a strain of E. Coli bacteria to ferment alcohols with carbon chains between 5 and 8 carbons in length. Butanol has only 4 carbons, and ethanol has but 2. Lowly methanol has only one carbon. Besides having more energy per gallon, the longer chain alcohols will be easily separated from water, negating the need for the expensive distillation step required by ethanol.

Liao and his colleagues use synthetic-biology tools to tinker with the amino acid metabolism of E. coli. All organisms produce a large number of amino acids, which are the building blocks of proteins. The researchers reengineer this metabolic pathway so that toward the end, the precursor compounds that would normally get converted into amino acids instead turn into long-chain alcohols.

To do this, the researchers insert genes into the bacteria that make them produce unnaturally long amino acid precursor molecules that have more than six carbon atoms. They also engineer two genes--one from a type of yeast, one from a cheese-making bacterium--into the microbe. These modified genes produce two new proteins that can convert the precursors into five-to-eight-carbon alcohols.

Startups LS9 and Amyris Biotechnologies are already reengineering microbes to produce hydrocarbon fuels. Both plan to begin commercial production of their fuels by 2010. _TechnologyReview

Very clever gene engineering. It will no doubt take time to scale up the process for higher yields and industrial quantities.

All the same, gene engineered micro-organisms stand to have the same revolutionary effect on biofuels production, eventually, that they are already having on pharmaceutical production. With some of the newer, less energy intensive processes, the largest expense after the physical plant will likely be feedstock. The ability to use minimally processed biomass as feedstock should allow such microbe produced biofuels to begin competing with petrofuels within the decade.