Removal of heavy metals using a brewer's yeast strain of Saccharomyces cerevisiae: advantages of using dead biomass

The capacities of live and heat-killed cells of Saccharomyces cerevisiae at 45°C for the removal of copper, nickel and zinc from the solution were compared. Kinetic studies have shown a maximum accumulation of Ni²⁺ and Zn²⁺ after 10 min for both types of cells, while for Cu²⁺ this was attained after 30 and 60 min for dead and live cells, respectively. Equilibrium studies have shown that inactivated biomass displayed a greater Zn²⁺ and Ni²⁺ accumulation than live yeasts. For Cu²⁺, live and dead cells showed similar accumulation. Fluorescence, scanning electron microscopy and infrared spectroscopy studies have shown that no appreciable structural or molecular changes occurred in the cells during the killing process. The increased metal uptake observed in dead cells can be most likely explained by the loss of membrane integrity, which allows the exposition of further metal-binding sites present inside the cells. Heat-killed cells showed a higher degree of heavy metal removal than live cells, being more suitable for further bioremediation works. Dead flocculent cells can be used in a low cost technology for detoxifying metal-bearing effluents as this approach combines an efficient metal removal with the ease of cell separation.