The Effect of Proanthocyanidins on Growth and Alcoholic Fermentation of Wine Yeast under Copper Stress

Proanthocyanidins (PAs) derived from the grape skin, as well as from grape seeds, grape stems, are an important group of polyphenols in wine. The aim of this study was to understand the effect of PAs (0.1, 1.0 g/L) on growth and alcoholic fermentation of 2 strains of Saccharomyces cerevisiae (commercial strain FREDDO and newly selected strain BH8) during copper-stress fermentation, using a simple model fermentation system. Our results showed that both PAs and Cu2+ could pose significant inhibition effects on the growth of yeast cells, CO2 release, sugar consumption, and ethanol production during the initial phase of the fermentation. Compared to PAs, Cu2+ performed more obvious inhibition on the yeast growth and fermentation. However, adding 1.0 g/L PAs increased in the vitality and metabolism activity of yeast cells at the mid-exponential phase of fermentation in the mediums with no copper and 0.1 mM Cu2+ added, shortened the period of wine fermentation, and decreased the copper residues. It indicated that PAs could improve the ability of wine yeast to resist detrimental effects under copper-stress fermentation condition, maintaining cells metabolic activity, and fermentation could be controlled by manipulating PAs supplementation. Practical Application Proanthocyanidins (PAs) derived from the grape's skin, grape seeds, and grape stems, could be macerated into wine during winemaking. PAs have been reported to have many beneficial biological activities. These experimental findings suggested PAs could improve the ability of wine yeast to resist detrimental effects of copper. Therefore, it will be helpful for further research on the mechanism of the beneficial effects of PAs on wine yeast under multiple stresses during winemaking.