Cellular surface characteristics of Saccharomyces cerevisiae before and after Ag(I) biosorption

The surface characteristics of Saccharomyces cerevisiae before and after Ag(I) biosorption were investigated by comprehensively using the scanning electron microscopy with the energy-dispersive X-ray analysis (SEM-EDX), the transmission electron microscopy with energy-dispersive X-ray analysis (TEM-EDX) and atomic force microscopy (AFM). The results showed that cell surface elements, surface topography and three-dimensional structures of S. cerevisiae changed after Ag(I) biosorption. SEM observation indicated that the appearances of Ag-adsorbed cells varied with initial Ag(I) concentration and contact time. TEM images observed Ag(I)-containing precipitates. AFM observation indicated that cells became smaller, and cell surface became smoother. The results of SEM-EDX, TEM-EDX, AFM and biosorption illustrated that Ag(I) was adsorbed onto the cell surface by covalent binding and ionic binding. P-, S- and O-containing groups on cell surface possibly contributed to the binding silver ions, and the N-containing components released from cells also probably contributed to Ag(I) biosorption.