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Applied and Environmental Microbiology, June 2006, p. 4207-4213, Vol. 72, No. 6
0099-2240/06/$08.00+0     doi:10.1128/AEM.02699-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Production of Xylitol from D-Xylose by a Xylitol Dehydrogenase Gene-Disrupted Mutant of Candida tropicalis

Byoung Sam Ko,1 Jinmi Kim,2 and Jung Hoe Kim1*

Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701,1 Department of Microbiology, School of Bioscience and Biotechnology, Chungnam National University, 220 Gung-dong, Yuseong-gu, Daejeon 305-764, Republic of Korea2

Received 15 November 2005/ Accepted 7 April 2006

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.

* Corresponding author. Mailing address: Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Korea. Phone: 82-42-869-2614. Fax: 82-42-869-5614. E-mail: kimjh{at}kaist.ac.kr.

Applied and Environmental Microbiology, June 2006, p. 4207-4213, Vol. 72, No. 6
0099-2240/06/$08.00+0     doi:10.1128/AEM.02699-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.





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