Heavy metal removal by yeast strains

Abstract

Cu'2+ removal from aqueous solutions (O.1mM) was compared using viable cells of two yeast strains, grown both in the presence and in the absence of the metal. The flocculent yeast strain (S. cerevisiae NRRL Y265) presented significantly higher removal yields in both cases (respectively, 62 and 99% versus 7 and 12% for the non-flocculent strain of S. carlsbergensis). The effect of the ion metal concentration on the biosorption capacity of S. cerevisiae NRRL Y265 was also tested in aqueous solutions of Cu 2'+, Cd'2+ and Pb2'+ ( 0.1, 0.25, 0.5 and 1mM). Cells were more efficient for Pb2'+ removal (90-100%) than for the others, being Cu 2'+ the least biosorbed ion. While for Pb 2' + there was no yield modification with concentration, for the other ·two ions a significant yield decrease was observed with the increase of ion concentration. On the contrary, in aqueous mixtures of two or three of these cations, only for the highest concentration tested (1mM) was a removal yield decrease observed. Similar data were obtained with non-viable cells of another flocculent yeast from a brewing. industry (UNICER). In every system analysed, Pb 2'+ was always preferentially removed, leading to the highest removal yields (85-100%). The best results were obtained with the flocculent S. cerevisiae strain from UNICER