Evaluation of selective uptake of selenium (Se(IV) and Se(VI)) and antimony (Sb(III) and Sb(V)) species by bakerʹs yeast cells (Saccharomyces cerevisiae)

Common bakerʹs yeast cells characterized as Saccharomyces cerevisiae were evaluated as a means of sequestering Se and Sb in different oxidation states (Se(IV), Se(VI), Sb(III) and Sb(V)) from aqueous solution. Several parameters affecting the degree of bioaccumulation of these elements were studied — solution pH, temperature, incubation time, and amount of biomass and analyte. The results obtained show that the biosorption process and its mechanism depend not only on the element but also on its oxidation state. In presence of yeast, aqueous Se(VI) remained unaltered and in solution under all the experimental conditions tested while Se(IV) is accumulated into the cell. The degree of accumulation depends on the amount of yeast, incubation time and temperature. Se(IV) is quantitatively bound to the yeast under the optimum conditions, i.e. 700 mg bakerʹs yeast, 30 min incubation time at pH 7.0 and 37 °C. The accumulation step may occur along with transformation processes of Se(IV), probably a reduction to Se(-II) species. Sb(III) was completely bound to the yeast cells at an incubation temperature of 60°C at pH 7, whereas Sb(V) showed less affinity and was unaffected under these conditions. The proposed method allows the specific sampling of Se and Sb species, which is especially important in environmental analysis since Sb(III) and Se(IV) are more toxic than Sb(V) and Se(VI), respectively.