Inhibition of the malolactic fermentation by Saccharomyces cerevisiae during the alcoholic fermentation.

摘要

The complex metabolic interactions that occur between wine yeast (Saccharomyces) and malolactic bacteria (Oenococcus oeni) during winemaking were investigated using a synthetic grape juice. Malolactic fermentation was induced in fermenting grape musts or wines inoculated with different commercial strains of S. cerevisiae. O. oeni was inhibited in wines that contained higher concentrations of total SO2 although strains UCD 522, RUBY.ferm, and UCLMS325 only inhibited the bacteria during fermentation under high nitrogen conditions. Strains Saint Georges S101 and EC1118 did not inhibit the bacteria and produced lower concentrations of SO2. Yeast produced higher amounts of SO 2 during fermentation under high nitrogen conditions suggesting that nitrogen affected the malolactic fermentation by influencing yeast SO 2 production. However, the production of SO2 by yeast did not always account for the inhibition of O. oeni. For example, S. cerevisiae strain RUBY.ferm inhibited the growth of O. oeni while strain EC1118 did not despite both strains producing similar amounts of SO2. However, the inhibition of the bacteria by RUBY.ferm was relieved if the wine was treated with proteases. Wine fermented by RUBY.ferm and the non-inhibitory yeast Saint Georges S101 was fractionated using ultrafiltration and each fraction was tested for its ability to inhibit O. oeni. RUBY.ferm wine containing substances between 3 and 5 kDa in size inhibited the growth of O. oeni while wine containing substances greater than 5 kDa in size did not. The inhibitory fraction of RUBY.ferm wine was analyzed by SDS PAGE and revealed a 5.9 kDa protein band present in wine fermented by RUBY.ferm that was not present in wine fermented by Saint Georges S101. The ability of the peptide to inhibit O. oeni seemed to be dependent on the presence of SO2 as the presence of the peptide alone was not sufficient to inhibit the bacteria if SO2 was present in low concentrations. It was therefore concluded that RUBY.ferm inhibited O. oeni through the production of both SO2 and an antibacterial peptide approximately 5.9 kDa in size.