Bacterium that makes alkanes

Last Updated : 20 September 2010, 10:39 IST

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A biotech company has won a patent on a genetically altered bacterium that converts sunlight and carbon dioxide into ingredients of diesel fuel, a step that could provide a new pathway for making ethanol or a diesel replacement that skips several cumbersome and expensive steps in existing methods.

The bacterium’s product, which it secretes like sweat, is a class of hydrocarbon molecules called alkanes that are chemically indistinguishable from the ones made in oil refineries.

The organism can grow in bodies of water unfit for drinking or on land that is useless for farming, according to the company, Joule Unlimited of Cambridge, Mass.“We make very clean, sulfur-free hydrocarbons that drop directly into the existing infrastructure for the production of diesel fuel,” said William J Sims, the chief executive of Joule.

‘Viable replacement’ for fossil fuels

The object, he said, was not to be an alternative for fossil fuels, but “to become a viable replacement.” Joule said it was the first company to patent an organism that secretes hydrocarbon fuel made continuously, directly from sunlight. Other companies, including Amyris Biotechnologies of Emeryville, Calif., and LS9 of San Carlos, Calif., are working on organisms that will make fuel if fed sugar from corn or cellulosic sources, but Joule’s bacterium does not require any sugar. Another company, Aurora Algae of Alameda, Calif., said recently that it had developed an algae-based platform for production of fuel, pharmaceuticals and other valuable chemicals. Development of a photosynthetic organism to make hydrocarbons is “an important step,” said Eric J Toone, the deputy director for technology at the Advanced Research Projects Agency-Energy, a new agency within the US Energy Department that makes grants for high-risk, high-reward projects.

But Toone and others cautioned that there were other steps to be mastered before such a technology could be commercialised.

The organism is a cyanobacterium, also known as blue-green algae, although it is technically not an algae. It produces the fuel using photosynthesis, the process that plants use to make sugars and other materials from water, carbon dioxide and sunlight.

Alternative energy experts agree that photosynthesis is a promising avenue for biofuel research.

The challenge is turning the resulting product into a fuel. Many companies are trying to develop an algae to do that job. But it requires energy to separate the algae from the water and then process the oil they make internally into a usable fuel. An organism that secretes the desired product directly avoids both problems. In a test in Leander, Texas, Joule’s bacteria strain produced ethanol.

Different variants can also make polymers and other high-value chemicals that are ordinarily derived from petroleum, according to Joule. The system can run on the carbon dioxide in ordinary air but will do better using the exhaust from a power plant, once pollutants like sulfur and nitrogen oxides have been removed, according to the company.

Joule said it would begin construction next year on a commercial plant, which it hopes will begin operations in 2012. The company predicts a yield of 15,000 gallons of diesel components per acre – far more fuel than an acre of corn grown for ethanol can produce.

Sims says the pilot project covers a little less than five acres. Because the process is modular, he said, a full-scale factory would simply mean making multiple copies of a smaller setup. And with a small amount of refining, he said, the hydrocarbons can be converted to an ingredient of jet fuel. An independent expert, Matthew C Posewitz, a professor at the Colorado School of Mines, said that making an organism that secreted hydrocarbons was “definitely one of the most active areas in the whole game right now.”

He said that Joule did not yet have a proved process, but that it had strong research and development capabilities.“They have some extreme horsepower within that company,” he said.

Published 20 September 2010, 10:39 IST

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