Abstract:

【Objective】 The research aimed to clarify the mechanism and differences of the fermentation behaviour between the model synthetic medium (MSM) and Cabernet Sauvignon grape must under copper stress.【Method】 In the present work, the influence of Cu2+ stress on Saccharomyces cerevisiae activity and the fermentation processes were studied in the MSM and Cabernet Sauvignon grape fermentation must. CuSO4 was added into the medium to achieve 0.05 mmol?L-1 and 0.50 mmol?L-1 Cu2+ concentrations. 【Result】 Cu2 + stress decreased the yeast viability in the two fermentation mediums. For the MSM, the fermentation of Saccharomyces cerevisiae was severely inhibited in the presence of 0.05 mmol?L-1 Cu2+. The yields of CO2 and ethanol were, respectively, 26.47% and 30.76% of the control and also the utilization of reduced sugar decreased apparently. While 0.05 mmol?L-1 Cu2+ stress had little effects on Cabernet Sauvignon grape must fermentation. The fermentation of MSM was totally inhibited under 0.50 mmol?L-1 Cu2+ stress. In the Cabernet Sauvignon grape must fermentation, only minor effects were observed in the presence of 0.50 mmol?L-1 Cu2 +, which had no statistically significant differences compared to the control. There was no difference of copper concentration in MSM before and after fermentation, while the copper concentration in Cabernet Sauvignon grape must was significantly decreased after fermentation. 【Conclusion】 Copper stress could decrease the yeast viability and inhibit the utilization of reducing sugar, thus resulted in the decreased yield of CO2 and ethanol apparently. The yeast in Cabernet Sauvignon grape must had higher resistance to Cu2 + than that in MSM. One reason may be contributed to the absorption of Cu2 + by the grape residue.

Key words: copper, model synthetic medium, Cabernet Sauvignon grape must, fermentation