Sugar Into Diesel
Engineers from the MIT were able to genetically reprogram a strain of yeast to convert sugars to fats more efficiently. This advance could lead to the renewable production of high-energy fuels such as diesel.
The researchers were led by Gregory Stephanopoulos the Willard Henry Dow Professor of Chemical Engineering and Biotechnology at MIT. They modified the metabolic pathways of year that naturally produces large quantities of lipids to make them 30 percent more efficient.
According to Stephanopoulos, “We have rewired the metabolism of these microbes to make them capable of producing oils at very high yields,”
With this upgrade, the production of renewable high-energy fuels can now be economically feasible. Today the research team is working on additional improvements that can help get closer to that goal.
“What we’ve done is reach about 75 percent of this yeast’s potential, and there is an additional 25 percent that will be subject of follow-up work,” Stephanopoulos adds.
There are renewable fuels that are made from corn and are useful as gasoline additives for running cars, but for large vehicles like ships, trucks and airplanes, more powerful fuels such as diesel are needed.
“Diesel is the preferred fuel because of its high energy density and the high efficiency of the engines that run on diesel. The problem with diesel is that so far it is entirely made from fossil fuels.” Stephanopoulos said.
There have been efforts to develop engines that run on biodiesel that are made from used cooking oil and had some success. Unfortunately, cooking oil is a scarce and expensive fuel source. On the other hand, starches like sugar cane and corn are much cheaper and more abundant. However, they should first be converted into lipids and will then be turned into high-density fuels such as diesel.
To be able to achieve this product, the research team worked with a yeast named Yarrowia lipolytica, which is a yeast that naturally produces large quantities of lipids. The team focused on utilizing the electrons that are generated from the breakdown of the glucose.
They then transformed Yarrowia with synthetic pathways that convert surplus NADH, which is a product of glucose breakdown, into NADPH, which can be utilized to synthesize lipids. They then ended up testing more than a dozen modified synthetic pathways.
By using this pathway, the yeast cells will only require only two-thirds of the glucose that is needed by unmodified yeast cells to produce the same amount of oil. The researchers hope to make this process even more efficient than when using cornstarch. They are also searching for cheaper sources of plant material such as grass and agricultural waste.