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Gene XYL2 encoding xylitol dehydrogenase (XDH) from Pichia stipitis

"The gene XYL2 can express xylitol dehydrogenase,Xylitol is oxidized to xylulose under the action of xylitol dehydrogenase, which relies on NAD. The genomic XYL2 gene was isolated and the nucleotide sequence of the 1089 bp structural gene, and of adjacent non-coding regions, was determined. The XYL2 open-reading frame codes for a protein of 363 amino acids with a predicted molecular mass of 38.5 kDa. The XYL2 gene is actively expressed in S. cerevisiae transformants. In our project, we expressed the XYL1 and XYL2 genes ,which are associated with xylose metabolism in Saccharomyces cerevisiae EBY100.The whole process of xylose metabolism is as follows: Xylose is reduced to xylulose under the action of NADPH-dependent xylose reductase (xylosereductase XR). Xylitol is then oxidized to xylulose under the action of xylitol dehydrogenase, which relies on NAD. Xylulose is then phosphorylated by xylulokinase to form 5-phosphate xylose and then into the pentose phosphate pathway, PPP. The intermediate product of PPP pathway 6-phosphate glucose and 3-phosphoric acid glycerol aldehyde through glycolysis pathway to form pyruvate. L-lactate dehydrogenase and coenzyme NADH reduced pyruvate to L-lactic acid. Saccharomyces cerevisiae is not able to use xylose as a result of the lack of enzymes that convert xylose into xylose, but can use the isomers of xylose-xylulose. In Saccharomyces cerevisiae, Xylulose is also first phosphorylated to form 5-phosphate sugar, which enters the PPP pathway and forms lactic acid by glycolysis. We have constructed engineered bacteria that can use xylose as a carbon source, which can be used as xylose and fermented xylose to produce ethanol, which is the result of our experiment.

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[1]Yu, S., H. Jeppsson, and Barbel Hahnhagerdal. "Xylulose fermentation by Saccharomyces cerevisiae and xylose-fermenting yeast strains.." Applied Microbiology and Biotechnology (1995): 314-320. [2]Kötter, Peter, and M. Ciriacy. "Xylose fermentation by Saccharomyces cerevisiae." Applied Microbiology & Biotechnology 38.6(1993):776-783. In short，gene XYL2 encoding xylitol dehydrogenase (XDH) from Pichia

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