Production of xylitol from D-xylose by a xylitol dehydrogenase gene-disrupted mutant of Candida tropicalis.
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.
Ko
Byoung Sam
BS
Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Korea.
Kim
Jinmi
J
Kim
Jung Hoe
JH
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*
D003470:Culture Media; D017931:DNA Primers; D014994:Xylose; D050542:D-Xylulose Reductase; D014993:Xylitol