Lead (II) adsorption efficiency and mechanisms by a heavy metal-tolerant yeast Cystobasidium oligophagum QN-3

The lead resistance and adsorption capacity of Cystobasidium oligophagum QN-3 were studied. The strain exhibited high Pb ²⁺ resistance, withstanding concentrations up to 6,000 mg/L on PDA plates and 26,000 mg/L in liquid PDA medium. The Pb ²⁺ adsorption capacity of QN-3 was significantly affected by Pb ²⁺ concentration, temperature, pH, and incubation time. Scanning electron microscopy (SEM) revealed notable morphological changes after adsorption of Pb ²⁺ , including cell surface wrinkling and elongation. Fourier transform infrared spectroscopy (FTIR) identified key functional groups (–NH ₂ , -OH, C=O, COO-, P=O, C-N and -CH) on cell surface participating in Pb ²⁺ adsorption. Chemical modification of functional groups combined with zeta potential measurements at varying pH and Pb ²⁺ concentrations confirmed that electrostatic interactions and complexation were the predominant Pb ²⁺ adsorption mechanisms. Pb ²⁺ was primarily bound to the cell wall, with minimal intracellular accumulation. The decreased Pb ²⁺ uptake observed in the presence of metabolic inhibitor DCC suggested an ATP-dependent transport process following initial surface biosorption. Pretreatments including ultrasonication, boiling and alkaline treatment enhanced Pb ²⁺ adsorption efficiency. The exceptional Pb ²⁺ tolerance and adsorption capacity of Cystobasidium oligophagum QN-3 highlighted its potential for bioremediation applications.