High activity of xylose reductase and xylitol dehydrogenase improves xylose fermentation by recombinant <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> |
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Authors: | Kaisa Karhumaa Romain Fromanger Bärbel Hahn-Hägerdal Marie-F Gorwa-Grauslund |
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Institution: | (1) Department of Applied Microbiology, Lund University, P.O. Box 124, SE-22100 Lund, Sweden |
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Abstract: | Xylose fermentation performance was studied of a previously developed Saccharomyces cerevisiae strain TMB 3057, carrying high xylose reductase (XR) and xylitol dehydrogenase (XDH) activity, overexpressed non-oxidative
pentose phosphate pathway (PPP) and deletion of the aldose reductase gene GRE3. The fermentation performance of TMB 3057 was significantly improved by increased ethanol production and reduced xylitol
formation compared with the reference strain TMB 3001. The effects of the individual genetic modifications on xylose fermentation
were investigated by comparing five isogenic strains with single or combined modifications. All strains with high activity
of both XR and XDH had increased ethanol yields and significantly decreased xylitol yields. The presence of glucose further
reduced xylitol formation in all studied strains. High activity of the non-oxidative PPP improved the xylose consumption rate.
The results indicate that ethanolic xylose fermentation by recombinant S. cerevisiae expressing XR and XDH is governed by the efficiency by which xylose is introduced in the central metabolism. |
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