Cadmium binding characterization and mechanism of a newly isolated strainCystobasidium oligophagumQN-3

The aim of this study was to screen a strain for the removal of Cd(2+)from aqueous solution and investigate the characterization and mechanism of the Cd(2+)binding process. A novel strain of yeast showed high tolerance of cadmium, namelyCystobasidium oligophagumQN-3, was isolated from soils, which could resist 22,000 mg/L and 18,000 mg/L Cd(2+)on PDA (potato dextrose agar) plate and in PDA liquid medium, respectively. Cd(2+)binding experiment showed that the strain could remove Cd(2+)from aqueous solution effectively, the maximum Cd(2+)removal rate of 84.45% was achieved at initial Cd(2+)concentration 30 mg/L. Scanning electron microscopy (SEM) analysis revealed that sorption of Cd(2+)by cells could be associated with changes in the cell surface morphology. Fourier transform-infrared spectroscopy (FTIR) analysis confirmed the important role of the functional groups -OH, C(sic)O, -NH2, COO-, P(sic)O, and CH- on the cell surface in the binding of Cd2+. The comparison of the binding ability of different cellular parts indicated a significant role of the cell wall played in the Cd(2+)binding process. Pretreatment of the cells by boiling or ultrasonication could improve the biosorption capacity of QN-3. In addition, QN-3 exhibited selective and preferential property of binding capacity for other heavy metals, such as Pb2+, Cu2+, Cd2+, Zn2+, and Ni2+. These data suggested the promising use ofCystobasidium oligophagumQN-3 as an effective and friendly biosorbent for cadmium or other heavy metals decontamination in the environment.