After cellulose, xylan is the most abundant biomass material on Earth, and therefore represents an enormous potential source of stored solar energy for the production of advance biofuels. A major roadblock, however, has been extracting xylan from plant cell walls. Researchers with the U.S. Department of Energy (DOE)'s Joint BioEnergy Institute (JBEI) have taken a significant step towards removing this roadblock by identifying a gene in rice plants whose suppression improves both the extraction of xylan and the overall release of the sugars needed to make biofuels.
The newly identified gene dubbed XAX1 acts to make xylan less extractable from plant cell walls. JBEI researchers, working with a mutant variety of rice plant dubbed xax1 in which the XAX1 gene has been "knocked-out" found that not only was xylan more extractable, but saccharification the breakdown of carbohydrates into releasable sugars also improved by better than 60-percent. Increased saccharification is key to more efficient production of advanced biofuels.
"In identifying XAX1 as a xylan biosynthetic protein, the first enzyme known to be specific to grass xylan synthesis, we've shown that xylan can be modified so as to increase saccharification," says Henrik Scheller, who heads JBEI's Feedstocks Division and directs its Cell Wall Biosynthesis group, and also holds an appointment with Lawrence Berkeley National Laboratory (Berkeley Lab). "Our findings provide us with new insights into xylan synthesis and how xylan substitutions may be modified for increased biofuel generation."
Scheller is a co-author of a paper describing this work that has been published by the Proceedings of the National Academy of Sciences (PNAS). The paper is titled "XAX1 from glycosyltransferase family 61 mediates Xylosyl transfer to rice xylan." The corresponding author is Pamela Ronald, who holds joint appointments with JBEI and the University of California (UC) Davis. Other a
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DOE/Lawrence Berkeley National Laboratory