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Abstract Cofactor engineering, a vital part of metabolism engineering, changes the redox cofactor regeneration approach. Its main goal is to rebuild the components of metabolic products. The bioconversion of xylose for the production of ethanol is being studied intensively because ethanol is an alternative energy source and a potential liquid fuel. Saccharomyces cerevisiae has been traditionally used in producing ethanol from fermentable sugars but it cannot utilize xylose, only its isomer xylulose. Introduction of the xylose fermentation pathway from Pichia stipitis into S. cerevisiae enables xylose utilization in recombinant S. cerevisiae, but the ethanol yields of xylose fermentation with recombinant S. cerevisiae has been low and large amounts of the byproduct xylitol are produced. The major reason is that the catabolism of xylose with the fungal pathway leads an imbalance of redox cofactor. The process of the catabolism of xylose requires NADPH and NAD+, both of which have to be regenerated in separated processes. More and more attention has therefore focused on the redox cofactor balance in S. cerevisia. The research progress of cofactor engineering to solve the imbalance of redox cofactor in xylose metabolism recombinant S. cerevisiae was introduced. This included expression of transhydrogenase, increasing the utilization of NADPH, and achieving the anaerobic reoxidation of NADH. Reversing the cofactor specificity of enzymes is another effective way.
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Received: 09 February 2006
Published: 25 February 2006
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