The incidence of killer activity of non-Saccharomyces yeasts towards indigenous yeast species of grape must: potential application in wine fermentation

Fourteen killer yeasts were assayed for their ability to kill species of ye ast that are commonly associated with fermenting grape must and wine. A tot al of 147 of a possible 364 killer-sensitive interactions were observed at pH 4.5. Of the killer yeasts studied, Pichia anomala NCYC 434 displayed the broadest killing range. At a pH value comparable with those of wine fermen ts, pH 3.5, the incidence of killer-sensitive interactions was reduced by 7 0% across all the yeasts. Williopsis saturnus var.,mrakii CBS 1707 exhibite d the broadest killing range at the lower pH, killing more than half of the tester strains. Intraspecific variation in sensitivity to killer yeasts wa s observed in all species where more than one strain was tested. Also, in s trains of Pichia anomala, Kluyveromyces lactis and Pichia membranifaciens, the three species in which more than one killer yeast was analysed, intrasp ecific variation in killer activity was observed.