Chemical engineers at the Massachusetts Institute of Technology have genetically reprogrammed a strain of yeast so that it converts sugars to fats more efficiently, and thus could lead to one of the first bio-based diesel fuels.

Renewable fuels like ethanol made from corn, sugar cane or other crops are useful as gasoline additives for cars. But for large vehicles such as trucks, airplanes and ships, more powerful fuels such as diesel are required.

MIT’s genetically modified yeast could make production of renewable high-energy fuels like diesel economically feasible. Image Credit: Jose-Luis Olivares/MIT “Diesel is the preferred fuel because of its high energy density and the high efficiency of the engines that run on diesel,” says research leader Gregory Stephanopoulos, professor of chemical engineering and biology at MIT. “The problem with diesel is that so far it is entirely made from fossil fuels.”

Efforts to develop engines that run on bio-diesel made from used cooking oils have had some success, researchers say, but cooking oil is a relatively scarce and expensive fuel source. Starches such as sugar cane and corn are cheaper and more plentiful, but these carbohydrates must first be converted into lipids, which can then be turned into high-density fuels such as diesel.

What MIT researchers have done is to modify the metabolic pathways of a yeast known as Yarrowia lipolytica, which naturally produce large quantities of lipids, to make them about 30% more efficient.

“We have rewired the metabolism of these microbes to make them capable of producing oils at very high yields,” Stephanopoulos said.

The improved conversion process could make production of renewable high-energy fuels economically feasible, and the MIT team is now working on additional improvements that would help get even closer to that goal. “What we’ve done is reach about 75% of this yeast’s potential, and there is an additional 25% that will be subject of follow-up work,” he says.