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Applied and Environmental Microbiology, September 2006, p. 5822-5828, Vol. 72, No. 9
0099-2240/06/$08.00+0 doi:10.1128/AEM.00750-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
UMR Sciences pour l'Oenologie, Microbiologie, INRA, F-34060 Montpellier Cedex 1, France,1 Laboratoire de Microbiologie, ENSBANA-Université de Bourgogne, F-21000 Dijon, France2
Received 31 March 2006/ Accepted 19 June 2006
We recently showed that expressing an H2O-NADH oxidase in Saccharomyces cerevisiae drastically reduces the intracellular NADH concentration and substantially alters the distribution of metabolic fluxes in the cell. Although the engineered strain produces a reduced amount of ethanol, a high level of acetaldehyde accumulates early in the process (1 g/liter), impairing growth and fermentation performance. To overcome these undesirable effects, we carried out a comprehensive analysis of the impact of oxygen on the metabolic network of the same NADH oxidase-expressing strain. While reducing the oxygen transfer rate led to a gradual recovery of the growth and fermentation performance, its impact on the ethanol yield was negligible. In contrast, supplying oxygen only during the stationary phase resulted in a 7% reduction in the ethanol yield, but without affecting growth and fermentation. This approach thus represents an effective strategy for producing wine with reduced levels of alcohol. Importantly, our data also point to a significant role for NAD+ reoxidation in controlling the glycolytic flux, indicating that engineered yeast strains expressing an NADH oxidase can be used as a powerful tool for gaining insight into redox metabolism in yeast.
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