[Mechanism of interaction between Ag+ and Saccharomyces cerevisiae].

To understand the characteristics of Ag+ biosorption by the waste biomass of Saccharomyces cerevisiae, the release phenomena of the cell physiological cations, such as K+, Mg2+, Ca2+, Na+, and pH value change during Ag+ uptake were investigated. The presence of Ag+ promoted the release of the cations, and decreased the absorption of H+. Ion exchange was one of the mechanisms involved in metal-microbe interaction. Ag+ also exhibited a degree covalent binding with the biomass. Both Ag+ uptake and cation release (K+, Mg2+, Ca2+ or Na+) followed the pseudo-second order kinetics. Fourier transform infrared spectroscopy (FTIR) indicated that the carboxyl group on the surface of the cells could play important role in metal-microbe interaction. The scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX) and transmission electron microscopy with energy-dispersive X-ray analysis (TEM-EDX) were used to directly observe the change of the component elements and surface configuration of the cells before and after the interaction of the microbe with Ag+, and the results proved that Ag+ was adsorbed by the cell surface. Simultaneously, the precipitate containing Ag with higher concentration than the surface-adsorbed Ag was formed on the cell surface also resulted in the removal of Ag+ from the aqueous solution.