Biofuel is produced through microbial fermentation of biomass crops, which yield the alcohol-based fuels ethanol and iso-butanol if yeast is used as the microbe to convert sugars from biomass into biofuels.

“However, at a certain concentration, the biofuels that are being created become toxic to the yeast used in making them. Our goal was to find a gene or genes that reduce this toxic effect,” says Yong-Su Jin, an Assistant Professor of Microbial Genomics in the U of I Department of Food Science and Human Nutrition.

Jin worked with Saccharomyces cerevisiae, the microbe most often used in making ethanol, to identify four genes (MSN2, DOG1, HAL1, and INO1) that improve tolerance to ethanol and iso-butanol when they are over-expressed.

“We expect these genes will serve as key components of a genetic toolbox for breeding yeast with high ethanol tolerance for efficient ethanol fermentation,” he says.

Over-expression of any of the four genes increased ethanol tolerance, but the strain in which INO1 was over-expressed elicited the highest ethanol yield and productivity – with increases of more than 70% for ethanol volume and more than 340% for ethanol tolerance when compared to the control strain.

“Identification of these genes should enable us to produce transportation fuels from biomass more economically and efficiently. It’s a first step in understanding the cellular reaction that currently limits the production process,” Jin explains.

Further study of these genes should increase alcohol tolerance even further, and that could translate into cost savings and greater efficiency during biofuel production, he adds.