Effect of Cr(III) compounds on yeasts survival

Abstract

Chromium plays an important role in yeast metabolism, where its form and concentration in the micro- and macroenvironment of the yeasts are the crucial factors. The tolerance of yeasts Saccharomyces cerevisiae ZIM 753 (Industrial culture collection, Biotechnical faculty, Ljubljana), Saccharomyces diastaticus ZIM 152 and Candida intermedia ZIM 156 on Cr(III) compounds such as CrCl3×6H2O, Cr(CH3COO)3, KCr(C2O4)2×3H2O, Cr(NO3)3×9H2O, CrK(SO4)2×12H2O, Cr-citrate in concentration range between 0,1 and 200 mM Cr(III) was determined. Yeast cells were propagated in malt extract liquid medium to the early stationary phase, the biomass was washed and resuspended in the MES buffer (pH = 4.0). After addition of Cr(III) compounds in different concentrations the suspension was shaked 24 hours by 28 °C. The survival of yeasts was determined by the CFU (collony forming unit) method on malt extract agar. The results indicate that the tolerance of yeasts to higher Cr(III) concentrations depends on the genera or the species of yeasts. However, the form of Cr(III) or Cr(III) compound, the yeasts were exposed to, is also the factor, which influences yeast survival.