A team of researchers from the Cockrell School of Engineering at The University of Texas at Austin have developed a new, mutant yeast strain that could lead to a more efficient and economical biofuel production process, and from non-food sources.
Hal Alper, Associate Professor in the McKetta Department of Chemical Engineering, and his team engineered a special type of yeast cell, Yarrowia lipolytica, to significantly enhance its ability to convert simple sugars into lipids that could then be used in place of petroleum-derived products.
“Our re-engineered strain serves as a stepping stone toward sustainable and renewable production of fuels such as biodiesel,” Alper said.
Previously, the team successfully combined genetically engineered yeast cells with ordinary table sugar to produce what Alper described as “a renewable version of sweet crude,” the premium form of petroleum. Building upon that approach, “a combination of evolutionary engineering strategies” was used to create the new strain of Yarrowia that produces 1.6 times as many lipids as their previous strain in a shorter time, reaching levels of 40 grams per liter, a concentration that could make yeast cells a viable platform in the creation of biofuels. The strain’s high lipid yield makes it one of the most efficient organisms for turning sugar into lipids. In addition, the resulting cells produced these lipids at a rate that was more than 2.5 times as fast as the previous strain.
“This significant improvement in our cell-based platform enables these cells to compete in the biofuels industry,” Alper said. “We have moved to concentration values that begin to align with those in other industrial fuel processes.”
Alper and his team improved the performance of Yarrowia through a combination of metabolic engineering and directed evolution, which involves mutation and selection to identify and cultivate the high-performing cells. The researchers recognized that cells with high lipid content would float to the top of a tube, whereas cells with lower lipid content would settle down to the bottom. The researchers used this “floating cell scheme” to identify the best-performing cells. Researchers used those high-performing cells, which produced more lipids and at a faster rate, to obtain the final yeast.
In addition to using lipids for biofuels, the cell-based platform is able to produce oleochemicals, including nutritional polyunsaturated fatty acids, waxes, lubricants, oils, and industrial solvents.
The researchers’ method and platform are patent pending. Alper’s lab is continuing to work on ways to improve how the yeast strain converts sugar into lipids, and on the types of lipid products they can produce.