Adsorption properties of lead and cadmium by Aureobasidium pullulans JB16

Abstract:

[Objective] To isolate and identify a heavy metal-resistant strain in the polluted soil and explore the factors influencing the adsorption of the strain for lead and cadmium under different conditions. [Methods] The strain was identified based on physiological and biochemical characteristics and ITS sequence. The streak plate method was employed to determine the maximum lead and cadmium tolerance of the strain and to explore the optimal conditions for the adsorption of lead and cadmium. The adsorption process was studied by pseudo-second-order kinetics, Langmuir and Freundlich models, and infrared spectroscopy. [Results] Strain JB16 was isolated and identified as Aureobasidium pullulans, which can tolerate the maximum lead concentration of 1 500 mg/L, the maximum cadmium concentration of 750 mg/L, and the maximum lead-cadmium mixture concentration of 1 500 mg/L and 300 mg/L, respectively. The single factor experiments (temperature, time, cell age, pH, wet mycelial concentration, and initial heavy metal concentration) optimized the lead adsorption conditions as follows: 30 ℃, 2 h, cell age of 72 h, pH 6, wet mycelial concentration of 5 g/L, and initial lead concentration of 150 mg/L, under which the adsorption rate of lead was 88.5%. The optimum conditions for cadmium adsorption: 30 ℃, 1 h, cell age of 96 h, pH 6, wet mycelial concentration of 5 g/L, and initial cadmium concentration of 20 mg/L, under which the adsorption rate of cadmium was 59.4%. The adsorption process of lead and cadmium by the strain conformed to the Langmuir model and the pseudo-second-order kinetic model, which indicated surface monolayer adsorption. The results of scanning electron microscopy and infrared spectroscopy demonstrated that the heavy metal ions changed the morphology of the strain, and the hydroxyl, carboxyl, saturated C-H bonds, and amide groups on the cell surface participated in the adsorption. [Conclusion] Strain JB16 can adsorb lead and cadmium, which enriches the strain resources and provides data support for the remediation of water and soil contaminated by lead and cadmium.

Key words:lead and cadmium tolerant strain;adsorption properties;scanning electron microscopy;infrared spectroscopy