Stable expression of xylose reductase gene enhances xylitol production in recombinant Saccharomyces cerevisiae

Effects of the expression mode of the xylose reductase gene (XYL1) on xylitol production in recombinant Saccharomyces cerevisiae strains were investigated in batch and fed-batch cultures. The gene coding for xylose reductase (XR) was introduced into S. cerevisiae in two different ways: by using a δ-integration vector for chromosome-integration and a YRp-based episomal plasmid vector. The two expression systems showed the different pattern of xylitol production in a glucose-limited fed-batch culture as opposed to the similar profile in a batch culture. The recombinant S. cerevisiae strain harboring the XR gene in the chromosome yielded a 1.70-fold enhancement in xylitol productivity in the fed-batch culture compared with the YRp-based xylose reductase expression strain. Such an improvement for the integrated recombinant strain was supported by the fact that the mitotic stability of the XR gene along with its high expression level worked in a cooperative manner.