02/02/10

Soaring demand for the current mainstay source for biodiesels -- corn, sugar and other starchy crops -- has caused the prices of some staple foods to soar as farmland is turned over to fuel crops, and worsened deforestation.

One problem is that oil from plants must first be chemically transformed. To purify ethanol, for example, it must be distilled from a fermentation broth.

But biologists in the United States say they have invented a genetically-engineered version of a humble bacterium called Escherichia coli that could provide a cheaper, more effective alternative.

It feasts on the simple sugars found in wood chips, straw and other biomass waste and secretes molecules of fuel.

"We incorporated genes that enabled production of biodiesel directly," lead author Jay Keasling of Lawrence Berkeley National Laboratory in California said in an email to AFP.

"The engineered E. coli secretes the biodiesel from the cell, which means that we don't need to break open the cell to get the diesel out. This saves substantially on processing cost," Keasling explained.

In addition, "the biodiesel is insoluble in water, which means that it forms a separate phase when it is secreted from the engineered E. coli -- it floats to the top as any oil would. This also saves on processing costs."

The study, published in the British science journal Nature, is a "proof-of-concept" piece of research.