EVALUATION OF SELECTIVE UPTAKE OF SELENIUM (SE(IV) AND SE(VI)) AND ANTIMONY (SB(III) AND SB(V)) SPECIES BY BAKERS-YEAST CELLS (SACCHAROMYCES-CEREVISIAE)

Common baker's yeast cells characterized as Saccharomyces cerevisiae w ere evaluated as a means of sequestering Se and Sb in different oxidat ion states (Se(IV), Se(VI), Sb(III) and Sb(V)) from aqueous solution. Several parameters affecting the degree of bioaccumulation of these el ements were studied - solution pH, temperature, incubation time, and a mount of biomass and analyte. The results obtained show that the bioso rption process and its mechanism depend not only on the element but al so on its oxidation state. In presence of yeast, aqueous Se(VI) remain ed unaltered and in solution under all the experimental conditions tes ted while Se(IV) is accumulated into the cell. The degree of accumulat ion depends on the amount of yeast, incubation time and temperature. S e(IV) is quantitatively bound to the yeast under the optimum condition s, i.e. 700 mg baker's yeast, 30 min incubation time at pH 7.0 and 37 degrees C. The accumulation step may occur along with transformation p rocesses of Se(IV), probably a reduction to Se(-II) species. Sb(III) w as completely bound to the yeast cells at an incubation temperature of 60 degrees C at pH 7, whereas Sb(V) showed less affinity and was unaf fected under these conditions. The proposed method allows the specific sampling of Se and Sb species, which is especially important in envir onmental analysis since Sb(III) and Se(IV) are more toxic than Sb(V) a nd Se(VI), respectively.