New Yeast Strain Converts Sugars in Corn Cobs into Ethanol

Researchers at the Agricultural Research Service (ARS) of the US Department of Agriculture have identified a yeast strain that breaks down and ferments the sugars in corn cobs without the addition of costly enzyme.

The new Clavispora strain Y-50464 is a variant that was found to tolerate higher temperatures and presence of cob-derived compounds that interfere with yeast growth and fermentation. Its ability to thrive at higher temperatures would allow its utilization in simultaneous saccharification and fermentation (SSF), a one-step process in cellulosic ethanol production that combines releasing and fermenting sugars.

In an experiment that compared the strain Y-50464 with another strain Y-12632, the USDA-ARS researchers found that with Y-50464, fermentation was faster and ethanol yield was higher without the addition of enzyme beta-glucosidase, one of two enzymes needed for ethanol production from cellulose. The enzymes cellulase and beta-glucosidase are normally added to break down residues and extract sugars from the corn cobs after xylose has been extracted. The researchers found evidence of enzyme activity in Y-50464 extracts, but not in Y-12632 extracts. They later confirmed that Y-50464 contains a new form of beta-glucosidase.

The yeast strain Y-50464 opens an opportunity to eliminate the need for costly additional enzyme for cellulosic ethanol production. The researchers plan to continue exploring options for combining the desirable characteristics of this strain with additional enzymes to further improve bioprocessing for advanced biofuels production.