We have recently shown that ethanol yields in winemaking can be reduced by taking advantage of the
respiratory metabolism of some non-Saccharomyces yeast species. Using an orthogonal design we have
now addressed the impact of three environmental factors (temperature, nitrogen source, and oxygen
supply level) on the aerobic metabolism in synthetic must of Saccharomyces cerevisiae, Metschnikowia
pulcherrima, Kluyveromyces lactis, and Candida sake. An integrative parameter, Efficacy (efficacy for
alcohol level reduction) was designed to simplify comparisons between strains or growth conditions. It
integrates sugar consumption, ethanol yield, and acetic acid production data. We found a high relative
impact of nitrogen source availability and temperature, as compared to aeration conditions, for several
fermentation parameters, including ethanol yield. However, increasing oxygen supply showed a positive
impact in terms of alcohol reduction and Efficacy for all the strains tested. The best results across assays
were obtained for C. sake CBS 5093, with high sugar consumption rates, associated to low ethanol yields,
and very low acetic acid production. Processes involving this yeast strain would benefit from high
aeration levels and low nitrogen source availability; while fermentation temperatures would have little
impact on its Efficacy for alcohol level reduction.
We have recently shown that ethanol yields in winemaking can be reduced by taking advantage of therespiratory metabolism of some non-Saccharomyces yeast species. Using an orthogonal design we havenow addressed the impact of three environmental factors (temperature, nitrogen source, and oxygensupply level) on the aerobic metabolism in synthetic must of Saccharomyces cerevisiae, Metschnikowiapulcherrima, Kluyveromyces lactis, and Candida sake. An integrative parameter, Efficacy (efficacy foralcohol level reduction) was designed to simplify comparisons between strains or growth conditions. Itintegrates sugar consumption, ethanol yield, and acetic acid production data. We found a high relativeimpact of nitrogen source availability and temperature, as compared to aeration conditions, for severalfermentation parameters, including ethanol yield. However, increasing oxygen supply showed a positiveimpact in terms of alcohol reduction and Efficacy for all the strains tested. The best results across assayswere obtained for C. sake CBS 5093, with high sugar consumption rates, associated to low ethanol yields,and very low acetic acid production. Processes involving this yeast strain would benefit from highaeration levels and low nitrogen source availability; while fermentation temperatures would have littleimpact on its Efficacy for alcohol level reduction.
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