BIOACCUMULATION OF METAL-CATIONS BY SACCHAROMYCES-CEREVISIAE

Yeast cells are capable of accumulation of various heavy metals, preferentially accumulating those of potential toxicity and also those of value. They retain their ability to accumulate heavy metals under a wide range of ambient conditions. In the present study it was shown that yeast cells in suspension accumulate heavy metal cations such as Cu2+, Co2+, and Cd2+. The level of copper accumulation was dependent on the ambient metal concentration and was markedly inhibited by extremes of ambient pH. Temperature (5-40 degrees C) and the presence of the alkali metal sodium had much smaller effects on the level of copper accumulation. This suggests that in waste-waters of pH 5.0-9.0, yeast biomass could provide an effective bioaccumlator for removal and/or recovery of the metal. During bioaccumulation and subsequent processes it is necessary to retain the biomass. It was shown in the present study that this could be achieved by cell immobilization. Immobilization allowed for complete removal of Cu2+, Co2+, and Cd2+ from synthetic metal solutions. The immobilized material could be freed of metals by use of the chelating agent ethylenediamine tetraacetic acid (EDTA) and recycled for further bioaccumulation events with little loss of accumulation capacity.