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

Abstract

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.