Xylitol production by recombinant Saccharomyces cerevisiae

We obtained efficient conversion of xylose to xylitol by transforming Saccharomyces cerevisiae with the gene encoding the xylose reductase (XR) of Pichia stipitis CBS 6054. Comparison of the chromosomal and cDNA copies of the XYL1 gene showed that the genomic XYL1 contains no introns, and an XR monomer of 318 amino acids (35,985 D) is encoded by an open reading frame of 954 bp. The amino acid sequence of the P. stipitis XR is similar to several aldose reductases, suggesting that P. stipitis XR is part of the aldoketo reductase superfamily. S. cerevisiae transformed with the XYL1 gene gave over 95% conversion of xylose into xylitol, a yield not obtainable with natural xylose utilizing yeasts.