Xylitol production by recombinant Saccharomyces cerevisiae expressing the Pichia stipitis and Candida shehatae XYL1 genes |
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Authors: | R Govinden B Pillay W H van Zyl D Pillay |
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Institution: | (1) Department of Microbiology, University of Durban-Westville, P. Bag X54001, Durban, 4000, South Africa Tel.: +27-21-8083610 Fax: +27-21-8083611, ZA;(2) Department of Microbiology, University of Stellenbosch, Stellenbosch 7600, South Africa, ZA |
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Abstract: | The xylose reductase gene (XYL1) was isolated from Pichia stipitis and Candida shehatae, cloned into YEp-based vectors under the control of ADH2 and PGK1 promoter/terminator cassettes and introduced into Saccharomyces cerevisiae Y294 by electroporation. Shake-flask fermentations were carried out with 5% xylose and 1% galactose, glucose or maltose as
co-substrates. Xylose uptake was similar in both the recombinant strains when different co-substrates were used and slowed
once the co-substrate was depleted. The recombinant strains converted xylose to xylitol with yields approaching the theoretical
maxima. Xylitol production was most rapid when the co-substrate was still present. Approximately 50% of the xylose was not
metabolized due to the depletion of the co-substrate.
Received: 23 December 1999 / Received revision: 30 June 2000 / Accepted: 1 July 2000 |
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