Isolation and Characterization of a Variant Manganese Resistant Strain of Saccharomyces cerevisiae

Manganese contamination in water is one of the most serious problems in Southeast Asian countries, including Vietnam. Bioremediation using microorganisms, especially from the brewing yeast Saccharomyces cerevisiae, is expected to be a useful technique to remove manganese from contaminated water. Yeast strain S. cerevisiae BY4741 as the wild-type strain and some manganese-accumulating mutants bred from BY4741 were examined for cell growth and manganese accumulation in YPD liquid medium containing various concentrations of Mn²⁺.　Variants accumulating larger concentrations of manganese were isolated by the repeated screening of survivors in YPD media containing10mM Mn²⁺. Manganese was accumulated by the yeast cells during growth, but the growth of BY4741 was retarded with increasing Mn²⁺ concentrations and almost inhibited at 15mM Mn²⁺. One variant isolate, named IM3, showed no retardation of growth up to 15 mM Mn²⁺ and could absorb over 4-fold more manganese than the BY4741 strain. Effects of culture temperature and pH on the growth and manganese accumulation were analyzed for IM3. Maximum accumulation was shown at 30℃, pH 6.0 while the optimal growth was shown at 37℃, pH 5.0 - 7.0. Interestingly, IM3 could grow a little at pH 9.0 when manganese was added to the culture media, while it could not grow without the addition of manganese.