UT Austin researcher rewires yeast to produce 90 percent lipids
Researchers at The University of Texas at Austin’s Cockrell School of Engineering have developed a high lipid-producing variety of yeast from genetically engineered cells and ordinary table sugar. This yeast produces lipids that can be used for biodiesel production.
Assistant professor Hal Alper, in the Cockrell School’s Mc-Ketta Department of Chemical Engineering, along with his team of students, created the new cell-based platform. Given that the yeast cells grow on sugars, Alper calls the biofuel produced by this process “a renewable version of sweet crude.”
The researchers’ platform produces the highest concentration of oils and fats reported through fermentation, the process of culturing cells to convert sugar into products such as alcohol, gases or acids. This work was published in Nature Communications on Jan. 20.
The UT Austin research team was able to rewire yeast cells to enable up to 90 percent of the cell mass to become lipids, which can then be used to produce biodiesel.
“To put this in perspective, this lipid value is approaching the concentration seen in many industrial biochemical processes,” Alper says. “We took a starting yeast strain of Yarrowia lipolytica, and we’ve been able to convert it into a factory for oil directly from sugar. This work opens up a new platform for a renewable energy and chemical source.”
The biofuel the researchers formulated is similar in composition to biodiesel made from soybean oil. The advantages of using the yeast cells to produce commercial-grade biodiesel are that yeast cells can be grown anywhere, do not compete with land resources and are easier to genetically alter than other sources of biofuel.
“By genetically rewiring Yarrowia lipolytica, Alper and his research group have created a near-commercial biocatalyst that produces high levels of bio-oils during carbohydrate fermentation,” says Lonnie O. Ingram, director of the Florida Center for Renewable Chemicals and Fuels at the University of Florida. “This is a remarkable demonstration of the power of metabolic engineering.”
So far, high-level production of biofuels and renewable oils has been an elusive goal, but the researchers believe that industry-scale production is possible with their platform.
In a large-scale engineering effort spanning four years, the researchers genetically modified Yarrowia lipolytica by both removing and overexpressing specific genes that influence lipid production. In addition, the team identified optimum culturing conditions that differ from standard conditions. Traditional methods rely on nitrogen starvation to trick yeast cells into storing fat and materials. Alper’s research provides a mechanism for growing lipids without nitrogen starvation. The research has resulted in a technology for which UT Austin has applied for a patent.
“Our cells do not require that starvation,” Alper says. “That makes it extremely attractive from an industry production standpoint.”
The team increased lipid levels by nearly 60-fold from the starting point.