Enhancing Yeast to Ferment Ethanol from Sugars from Cellulosic Biomass

8 June 2006

Researchers at Delft University of Technology are genetically modifying Saccharomyces cerevisiae (baker’s yeast) to enable the anaerobic fermentation of xylose—a sugar derived from cellulosic material—as well as glucose into ethanol. Most fermentative yeasts cannot convert xylose into ethanol—that’s a bottleneck for the development of the production of cellulosic ethanol. Those yeasts that can don’t do so very effectively.

The Dutch team inserted a gene derived from a fungus (Piromyces) found in elephant feces into S. cerevisiae, and then subsequently improved the modification through evolutionary engineering.

Specific ethanol production from xylose by yeast over the last two decades. The most recent work by the Dutch team is represented by points 12 and 13.

Work on enhancing the ability of yeast to ferment xylose has been an area of focus for more than two decades. The use of evolutionary engineering by the team, led by Markos Kuyper (who just received his doctorate from TUD for this work), enabled a major leap forward in the productivity of the xylose-fermenting strains. (Chart at right.)

In our opinion, the fermentation performance of strain RWB 218 is such that, in principle, the kinetics of anaerobic xylose fermentation no longer present a true bottleneck in the fermentation of hemicellulose hydrolysates. However, this does not imply that further improvement is either impossible or undesirable.

...We expect that a combination of knowledge-based metabolic engineering and evolutionary engineering will enable further improvement of fermentation kinetics.

Delft University of Technology, the Kluyver Centre for Genomics of Industrial Fermentation, Royal Nedalco and BIRD Engineering are working together on furthering this project. These parties expect to achieve large-scale industrial implementation within 5 years.

Resources:

• “Evolutionary engineering of mixed-sugar utilization by a xylose-fermenting Saccharomyces cerevisiae strain”; Marko Kuyper, Maurice J. Toirkens, Jasper A. Diderich, Aaron A. Winkler, Johannes P. van Dijken, Jack T. Pronk; FEMS Yeast Research, Volume 5 Page 925–July 2005; doi:10.1016/j.femsyr.2005.04.004