BIOSORPTION OF HEAVY-METALS BY SACCHAROMYCES-CEREVISIAE

Abundant and common yeast biomass has been examined for its capacity t o sequester heavy metals from dilute aqueous solutions. Live and nonli ving biomass of Saccharomyces cerevisiae differs in the uptake of uran ium, zinc and copper at the optimum pH 4-5. Culture growth conditions can influence the biosorbent metal uptake capacity which normally was: living and non-living brewer's yeast: U > Zn > Cd > Cu; non-living ba ker's yeast: Zn > (Cd) > U > Cu; living baker's yeast: Zn > Cu approxi mate to (Cd)> U. Non-living brewer's yeast biomass accumulated 0.58 mm olU/g. The best biosorbent of zinc was non-living baker's yeast (appro ximate to 0.56 mmolZn/g). Dead cells of S. cerevisiae removed approxim ately 40% more uranium or zinc than the corresponding live cultures. B iosorption of uranium by S. cerevisiae was a rapid process reaching 60 % of the final uptake value within the first 15 min of contact. Its de position differing from that of other heavy metals more associated wit h the cell wall, uranium was deposited as fine needle-like crystals bo th on the inside and outside of the S. cerevisiae cells.