Xylose utilisation by recombinant strains of Saccharomyces cerevisiae on different carbon sources |
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Authors: | W H van Zyl A Eliasson T Hobley B Hahn-Hägerdal |
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Institution: | (1) Department of Microbiology, University of Stellenbosch, Stellenbosch 7600, South Africa e-mail: WHVZ@maties.sun.ac.za Tel.: +27-21-8083611 Fax: +27-21-8083611, ZA;(2) Department of Applied Microbiology, Lund University, S-22100 Lund, Sweden, SE |
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Abstract: | Autoselective xylose-utilising strains of Saccharomyces cerevisiae expressing the xylose reductase (XYL1) and xylitol dehydrogenase (XYL2) genes of Pichia stipitis were constructed by replacing the chromosomal FUR1 gene with a disrupted fur1::LEU2 allele. Anaerobic fermentations with 80 g l−1
d-xylose as substrate showed a twofold higher consumption of xylose in complex medium compared to defined medium. The xylose
consumption rate increased a further threefold when 20 g l−1
d-glucose or raffinose was used as co-substrate together with 50 g l−1
d-xylose. Xylose consumption was higher with raffinose as co-substrate than with glucose (85% versus 71%, respectively) after
82 h fermentations. A high initial ethanol concentration and moderate levels of glycerol and acetic acid accompanied glucose
as co-substrate, whereas the ethanol concentration gradually increased with raffinose as co-substrate with no glycerol and
much less acetic acid formation.
Received: 12 March 1999 / Received revision: 31 June 1999 / Accepted: 5 July 1999 |
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