title: Production of xylitol from D-xylose by a xylitol dehydrogenase gene-disrupted mutant of Candida tropicalis.
abstract: Xylitol dehydrogenase (XDH) is one of the key enzymes in d-xylose metabolism, catalyzing the oxidation of xylitol to d-xylulose. Two copies of the XYL2 gene encoding XDH in the diploid yeast Candida tropicalis were sequentially disrupted using the Ura-blasting method. The XYL2-disrupted mutant, BSXDH-3, did not grow on a minimal medium containing d-xylose as a sole carbon source. An enzyme assay experiment indicated that BSXDH-3 lost apparently all XDH activity. Xylitol production by BSXDH-3 was evaluated using a xylitol fermentation medium with glucose as a cosubstrate. As glucose was found to be an insufficient cosubstrate, various carbon sources were screened for efficient cofactor regeneration, and glycerol was found to be the best cosubstrate. BSXDH-3 produced xylitol with a volumetric productivity of 3.23 g liter(-1) h(-1), a specific productivity of 0.76 g g(-1) h(-1), and a xylitol yield of 98%. This is the first report of gene disruption of C. tropicalis for enhancing the efficiency of xylitol production.
authors.affiliation: Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Byoung Sam
authors.initials: BS
authors.lastname: Ko
authors.forename: Jinmi
authors.initials: J
authors.lastname: Kim
authors.forename: Jung Hoe
authors.initials: JH
authors.lastname: Kim
mesh_terms: D001483:Base Sequence; D041022:Candida tropicalis / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D003470:Culture Media; D050542:D-Xylulose Reductase / Q000235:genetics*; D017931:DNA Primers; D004171:Diploidy; D005800:Genes, Fungal; D007700:Kinetics; D009154:Mutation; D014993:Xylitol / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism*
chemical_list: D003470:Culture Media; D017931:DNA Primers; D014994:Xylose; D050542:D-Xylulose Reductase; D014993:Xylitol