ISOLATION AND CHARACTERIZATION OF NICKEL-ACCUMULATING YEASTS

We selected three yeast strains that efficiently remove heavy metal io ns from aqueous solution. We first screened yeasts that grew in the pr esence of 2 mM NiCl2 among our stock of wild yeasts, and then selected those that removed Ni most efficiently from aqueous solution. These s trains also removed Cu and Zn from aqueous solution and were identifie d as Candida species. Ni uptake was efficient at pH between 4.0 and 7. 0, but less efficient at pH below 3.0. The amount of Ni taken up by th e yeast cells was proportional to the initial concentration of NiCl2 b elow about 4 mM Ni. The cells retained the abilities to remove Ni afte r treatment with 10 mM EDTA or 1 M HCl for repeated usage, or after he at treatment.