The present study investigated the effect of Ca2+, Mg2+, Zn2+, Mn2+, Co2+ and Cu2+ on protein and trehalose synthesis, fermentation activity and biomass yield in two strains of baker's yeast Saccharomyces cerevisiae cultured on synthetic Rose's medium. The experiments showed an increase in trehalose content (by 15-60%) and fermentation activity (by 20-50%) in yeast cultured on the medium supplemented with Mg2+, Zn2+ and Mn2+. Ion pairs, and especially Zn2+ and Mn2+, exerted positive synergistic action on fermentation activity and volume of trehalose synthesis. The addition of Mn2+ or Zn2+ (10-20 µM) to the medium reduced negative effects of the increased concentrations of Cu2+ and Co2+ on the cells of the tested yeast.