Yeast respiration of sugars by non-Saccharomyces yeast species: a promising and barely explored approach to lowering alcohol content of wines

The increasing ethanol content is a major challenge imposed by climate change on the production of quality wines. We propose a strategy for lowering ethanol production during grape must fermentation by taking advantage of the differences in energy metabolism among ascomycetous wine yeast species. We hypothesize that using carefully selected yeast strains the available oxygen would be taken up by yeast cells for the respiration of a significant fraction of the hexoses present in grape must. The actual degree of sugar consumption by this pathway, and the concomitant reduction in the final ethanol yield, would depend among other factors on the amount of available oxygen, in turn depending on standard winemaking practices or ad hoc aeration regimes. Setting up this strategy would involve the birth of a new research field, integrating topics like quantitative analysis of the energy and overall metabolism of non- Saccharomyces yeast species under winemaking conditions, interactions between yeast strains of different species in the grape must environment, or the impact of eventual ad hoc oxygenation treatments on must and wine constituents.