Cadmium resistance, microbial biosorptive performance and mechanisms of a novel biocontrol bacterium Paenibacillus sp. LYX-1.

In this study, a novel biocontrol bacterium was isolated and identified as Paenibacillus sp. LYX-1 from soils in the peach orchard. Both Cd resistance and biosorption behavior of strain LYX-1 was explored. Meanwhile, the Cd resistance and biosorption mechanisms were further identified by Cd-resistant genes, SEM-EDS, FTIR, XPS, and TEM analysis. The results showed that strain LYX-1 could resist 50 mg/L Cd and had the CzcD gene responsible for Cd efflux. Under pH 8.0 and at a dose of 1.0 g/L sorbent dose, the removal efficiencies of living and dead cells were as high as 90.39% and 75.67% at 20 mg/L Cd, respectively. For the adsorption isotherm test, results revealed that both Langmuir (R = 0.9704) and Freundlich (R = 0.9915) model could describe the Cd biosorption well for living strain LYX-1. The maximum equilibrium biosorption capacities of living and dead biomass were 30.6790 and 24.3752 mg/g, respectively. In the adsorption kinetic test, the adsorption process of both living and dead strain LYX-1 all satisfied the pseudo-second kinetic equation. A desorption study showed that strain LYX-1 sorbents could be recycled and regenerated by eluents efficiently. SEM-EDS analysis reflected that Cd was bound to the cell wall. Besides, the biosorption process was controlled by chemisorption with the participation of the -OH, -NH, -C = O, O = C-O, C-N, S, and phosphate functional groups on the cell surface of strain LYX-1, which were identified by FTIR and XPS. Bioaccumulation also made a contribution to the Cd removal during the biosorption process of living sorbent. The above results indicated that strain LYX-1 had higher Cd tolerance and Cd removal capacity. This strain exhibits promising application to the removal of Cd in the Cd-contaminated environment.