BioTork develops xylose-fermenting yeast for ethanol facilities

By Kris Bevill | May 08, 2012

After nearly two years of collaborative research, biotechnology company BioTork LLC and the National Corn-to-Ethanol Research Center have developed a yeast strain capable of fermenting the xylose found in ligno-cellulosic biomass in a commercial-scale environment.

Xylose is the second most abundant sugar in ligno-cellulosic biomass but cannot be fermented by Saccharomyces cerevisiae, the predominant yeast used in ethanol production. The USDA had previously engineered a strain of S. cerevisiae capable of fermenting xylose, but the genetic engineering negatively impacted the strain’s growth rate, making it inapplicable for use in an industrial environment.  BioTork utilized proprietary continuous culture technology developed by Florida-based Evolugate LLC as part of an adaptive evolution method to essentially teach that strain to grow under industrialized settings. Xylose was placed in a medium with the yeast strain and the fittest yeast cells were then selected and re-introduced to increasing proportions of xylose over the course of several months until they eventually learned to grow on xylose alone.

“While improvements to the growth rate and initial scale-up of its performance in an industrial setting are underway, this strain has the potential to be one of the first economically viable xylose-fermenting strains, and represent a fruitful combination of genetic engineering and adaptive evolution,” Tom Lyons, BioTork chief scientific officer said in a news release.

Because D-xylose comprises up to 30 percent of cellulosic biomass, BioTork’s yeast strain could be applied to various types of biomass for cellulosic ethanol production but one of the first applications envisioned for the yeast strain, currently known only as SC48-EVG51, is to produce ethanol from distillers dried grains (DDGs) at existing corn ethanol facilities. According to BioTork, if the glucose and xylose in distillers grains were converted to ethanol, producers could increase their ethanol output by 10 percent without increasing their capital expenditures. “The sugar xylose represents close to 18 percent of the dry weight of distillers grains, and our partnership with NCERC has mostly solved the way to ferment it,” said Ziad Ghanimi, public relations manager at BioTork. While the U.S. ethanol industry is currently facing a domestic blendwall, Ghanimi noted that there continues to be demand internationally for increasing amounts of ethanol, which could provide the market for additional U.S. capacity.

BioTork does not plan to make the newly developed yeast commercially available in one standard strain for distillers grains-to-ethanol production, simply because the chemical composition of distillers grains varies from plant to plant, Ghanimi said. Instead, the company will optimize the strain for use with each specific product. Licensing fees will likewise vary, he said.

Funding for this research was provided by BioTork and the Illinois Renewable Fuels Research, Development and Demonstration Program, under the direction of the state commerce department. BioTork and the NCERC will continue to collaborate on ethanol-related research, focusing next on hydrolyzed corn fiber.