Despite the high energetic cost of the reduction of sulfate to H2S, required for the synthesis of sulfur-containing amino acids, some wine Saccharomyces cerevisiae strains have been reported to produce excessive amounts of H2S during alcoholic fermentation, which is detrimental to wine quality. 

Surprisingly, in the presence of sulfite, used as a preservative, wine strains produce more H2S than wild (oak) or wine velum (flor) isolates during fermentation. Since copper resistance caused by the amplification of the sulfur rich protein Cup1p is a specific adaptation trait of wine strains, the link between copper resistance mechanism, sulfur metabolism and H2S production was studied in this work.

It was shown that a higher content of copper in the must increases the production of H2S, and that SO2 increases the resistance to copper. Using a set of 51 strains we observed a positive and then negative relation between the number of copies of CUP1 and H2S production during fermentation.

The originality of this study thus lies in highlighting a little-known fact: the massive use of copper for grapevine protection has led to the selection of resistant strains at the cost of a metabolic compromise: an overproduction of H2S, maximized by the addition of sulfur, leading to a decrease in wine quality. This modification of wine profiles has led to an increase in the use of aeration practices through racking to counteract the appearance of these defects.

These results highlight the importance of understanding the mechanisms of yeast resistance and adaptation to optimize wine quality, particularly in a context where new climatic and sanitary requirements force the modification of oenological and grapevine cultivation practices.

Reference article:
De Guidi, I., Galeote, V., Blondin, B. et al. Copper-based grape pest management has impacted wine aroma. Sci Rep 14, 10124 (2024)