A comparative study on Pb2+ accumulation between Saccharomyces cerevisiae and Aureobasidium pullulans by SEM (scanning electron microscopy) and EDX (energy dispersive X-ray) analyses

Scanning electron microscopy and energy dispersive X-ray analyses were carr ied out in a comparative investigation of Pb2+ accumulation in Saccharomyce s cerevisiae and Aureobasidium pullulans. In S. cerevisiae, the time requir ed to reach an equilibrium state was shortened from 100 h to 1h as the init ial Pb2+ concentration decreased from 96.5 mg/l to 16.0 mg/l, whereas the t ime was almost independent of initial Pb2+ concentration in A. pullulans. C oncomitant with the Pb2+ accumulation, the cell surface of S. cerevisiae be came rough and the amounts of potassium, phosphorus and sulfur on the cell surface decreased. However, significant increase of Pb2+ on the cell surfac e after Pb2+ accumulation was not observed due to Pb2+ penetration into the cell interior. In contrast, the Pb2+ accumulation had no significant effec t on the surface characteristics of A. pullulans and extreme Pb2+ accumulat ion was observed on the cell surface because Pb2+ could not penetrate into the cell interior due to the existence of extracellular polymeric substance s.