Copper impact on Saccharomyces cerevisiae during wine fermentation: interplay between strain effect and temperature modulation

Abstract Copper-based products are widely used for disease control in organic vineyards, however, copper residues in grape must may affect alcoholic fermentation and final wine composition. This study aimed to evaluate how copper affects yeast fermentation performance and final fermentation-related metabolites, and whether these effects depend on yeast strain and fermentation temperature. A two-stage experimental approach was adopted. First, sixteen commercial Saccharomyces cerevisiae strains were fermented in two natural musts with or without copper addition to assess strain-dependent responses under natural grape must conditions. Then, selected strains showing contrasting copper responses were fermented in synthetic must at 16, 18, and 20 °C to evaluate the interaction between strain, copper, and temperature under controlled conditions. Copper affected fermentation kinetics in a strain-dependent manner, leading to delayed or incomplete fermentation depending on the yeast and must. Copper also promoted acetaldehyde accumulation, although this response did not always parallel the degree of fermentation inhibition. In synthetic must, copper tolerance differed clearly among the selected strains, and increasing fermentation temperature did not consistently reduce copper inhibition. Copper also altered final metabolite composition, with acetaldehyde showing the most consistent increase, whereas free and total sulfur dioxide and acetic acid showed more variable responses depending on yeast strain and fermentation temperature. Overall, these findings show that the impact of copper on alcoholic fermentation depends on the interaction between yeast strain and fermentation temperature, highlighting the importance of selecting copper-tolerant strains and carefully managing fermentation conditions in copper-rich musts.