A Comparative Study on Pb~(2+) Accumulation between Saccharomyces cerevisiae and Aureobasidium pullulans by SEM (Scanning Electron Microscopy) and EDX (Energy Dispersive X-ray) Analyses

摘要

Scanning electron microscopy and energy dispersive X-ray analyses were carried out in a comparative investigation of Pb~(2+) accumulation in Saccharomyces cerevisiae and Aureobasidium pullulans. In S. cerevisiae, the time required to reach an equilibrium state was shortened from 100 h to 1 h as the initial Pb~(2+) concentration decreased from 96.5 mg/l to 16.0 mg/l, whereas the time was almost independent of initial Pb~(2+) concentration in A. pullulans. Concomitant with the Pb~(2+) accumulation, the cell surface of S. cerevisiae became rough and the amounts of potassium, phosphorus and sulfur on the cell surface decreased. However, significant increase of Pb~(2+) on the cell surface after Pb~(2+) accumulation was not observed due to Pb~(2+) penetration into the cell interior. In contrast, the Pb~(2+) accumulation had no significant effect on the surface characteristics of A. pullulans and extreme Pb~(2+) accumulation was observed on the cell surface because Pb~(2+) could not penetrate into the cell interior due to the existence of extracellular polymeric substances.