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Enhancing Yeast to Ferment Ethanol from Sugars from Cellulosic Biomass

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.



tom deplume

Does the chart mean nearly 10 times more ethanol from the feedstock?


It means that the strain--when grown on a synthetic medium--can produce nearly 10 times more ethanol from xylose than other strains. So it's a very positive development for that approach, but it's still a starting point.

There's still a good deal of ground to cover between this and a cost-effective industrial process--including the pretreatment of the cellulosic biomass to release the sugars. (Hence the estimate of 5 years.) Ultimate yield TBD.

Rafael Seild

Great news from my alma mater. I suspect the 5-year horizon may be a little aggressive, it takes a long time to get building permits for any large-scale petrochemical installation. Especially one involving GM technology in Europe.

Even if the Dutch public is eager for affordable renewable fuels (don't know), the team will still need to prove that their yeast strain cannot cause any damage if it is ever inadvertently released into the environment. I hope that proves a fairly easy hurdle to take.

Gregory Gottsacker

Samuel Adams Brewing Company has developed a "ninja" yeast for brewing beer that produces alcohol yields over 25% using conventional beer brewing ingredients. I assume that their work was to develop a yeast that didn't die as easily as conventional brewing yeasts when exposed to high concentrations of alcohol. Researchers should be looking into this technology, as well, to increase ethanol yields for biofuel.

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