Thermotolerant yeast can provide more climate-smart etanol

With a simple mutation, yeast can grow in higher than normal temperatures. Researchers at Chalmers University of Technology demonstrate this in an article to be published in the scientific journal Science. 

The findings may result in ethanol being more effectively manufactured for vehicle fuel, as well as increase the possibility of using residual waste as a raw material. If industrial yeast cultivation is not cooled, the yeast cells die from the heat they themselves produce. Yeast cultivation is currently cooled to 30 degrees, the temperature at which the yeast cells can best do their job – producing ethanol.

However, the production of bioethanol could be both less expensive and more effective if the temperature could be maintained at 40 degrees. A great deal of money could be saved on the cooling costs, and the risk of bacterial growth would decrease. In addition, the raw material, for example starch, must be broken down into sugars that the yeast can use, a process that functions best at high temperatures.

Researchers at Chalmers University of Technology have now resolved the issue of what makes yeast thermotolerant. "As it turns out, a simple mutation is sufficient," says Jens Nielsen, professor of systems biology and head of the research team. "Yeast has a molecule in its cell membrane called ergosterol, instead of cholesterol which humans have. The mutation exchanges ergosterol for a more bent molecule called fecosterol. This has several different effects on the cells, which enables the yeast to grow at 40 degrees. "