Impact of sulphur dioxide on the viability, culturability, and volatile phenol production of Dekkera bruxellensis in wine

Viability and culturability of eight Dekkera bruxellensis strains in wine along with volatile phenols accumulation in response to increasing concentrations of molecular SO2 (mSO2) were investigated. mSO2 concentrations up to 1 mg/L induced the non-culturable state of a portion of the population in all the strains to a different extent for each strains, although the cells were still viable. At 1.4 mg/L mSO2 cells were non-culturable, though 0.38-29.01% of cells retained their viability. When exposed to 2.1 m/L mSO2, viable cells were not detected. Up to 0.24 mg/L of 4-vinylguaiacol and up to 0.73 mg/L of 4-ethylphenol were accumulated by non-culturable and dead Dekkera bruxellensis strains. The concentration of mSO2 needed for the transition from viable to non-culturable state of D. bruxellensis strains was higher in wine than in synthetic wine medium. The volatile phenols accumulated in wine were different from those produced in synthetic wine medium, although their accumulation kinetics was similar.