USDA Researchers Modifying Yeast for Cellulosic Ethanol Production
29 November 2005
|L. edodes, source of the gene for xylanase|
Researchers at the USDA Agricultural Research Service have cloned a gene from the Shiitake mushroom and are using that as the mechanism for yeast or other organisms to be able to process cellulosic biomass for ethanol production.
The dominant technology for ethanol production is the fermentation of sugars from sugary plants or from plant starches converted to sugar. For cellulosic biomass to function as an ethanol feedstock, the cellulose must first be converted to fermentable sugars.
(Gasification of cellulosic biomass and then the subsequent catalytic conversion to ethanol is also a possible production route, but not one under much current consideration.)
Shiitake mushrooms (Lentinula edodes) typically grow on downed wood in the forest, converting the cellulosic material into sugars they use for food.
The Xyn11A gene carries the instructions that the mushroom uses to make the enzyme xylanase, which breaks down xylan, one of the main components of hemicellulose.
The ARS researchers transferred the Xyn11A gene into yeast. Equipped with the gene, the yeast was able to produce xylanase. In nature, the yeast normally can’t do that.
Next, the scientists will work on engineering the mushroom gene to optimize the volume and rate of production of xylanse to better determine its suitability for a commercial cellulosic ethanol process.
“Cloning and Characterization of the Xyn11A Gene from Lentinula edodes”; Charles C. Lee, Dominic W. S. Wong and George H. Robertson; The Protein Journal; Volume 24, Number 1, January 2005, pp. 21–26; DOI: 10.1007/s10930-004-0602-0
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