Vogelbusch Optimizes Yeast for Higher-Yield Fermentation Process for Cellulosic Ethanol

29 March 2008

Austria-based Vogelbusch GmbH has developed and is seeking a patent on an efficient fermentation process for the high-yield extraction of bioethanol from materials containing hemicellulose using an optimized strain of the yeast Saccharomyces cerevisiae.

Working in partnership with the Institute of Biotechnology and Biochemical Engineering at Graz University of Technology, the company says it has succeeded in extracting “significantly more” ethanol from this raw material than other processes.

The focus of the research was to optimize the process that converts the carbohydrate xylose into ethanol using the yeast S. cerevisiae. Xylose is a key intermediate in the production of bioethanol from wood waste, but production processes based on this material are usually relatively inefficient. The reason for this is the imbalanced availability of the substances NAD and NADP—which function as co-enzymes during the conversion process and transfer hydrogen groups—in the majority of microorganisms.

The optimization work that Vogelbusch has carried out on S. cerevisiae resolves the issue of co-enzyme imbalance, thereby delivering greater efficiency in the conversion of xylose into ethanol. Vogelbusch made the following modifications to S. cerevisiae:

• Introduced the capacity to synthesize a form of the enzyme xylose reductase with an altered binding site for certain co-enzymes.

• Introduced the capacity from the yeast Galactocandida mastotermitis to synthesize the enzyme xylitol dehydrogenase.

• Introduced the capacity to synthesize larger volumes of the enzyme xylulosekinase.

The increased efficiency levels in xylose-based ethanol production thus achieved also help to lower the production of unwanted by-products such as glycerine and xylitol. As a result, this optimized strain of S. cerevisiae is able to produce greater ethanol yields than other previously used strains, according to Vogelbusch.