Removal of cadmium, nickel, copper, and zinc ions from water by Agromyces sp. CS16

Abstract:

[Objective] A potential new actinomycete strain Agromyces sp. CS16 was isolated from the surface soil of the mangrove in Futian, Shenzhen. We studied the capacity and application of the strain in the removal of heavy metals from water, aiming to provide technical support for the bioremediation of heavy metal-polluted water. [Methods] The capacity of strain CS16 in removing Cd²⁺, Ni²⁺, Cu²⁺, and Zn²⁺, and the extracellular and intracellular removal rates of the metal ions were determined. Moreover, the whole genome sequencing was performed to identify the genes associated with the heavy metal tolerance in strain CS16. Furthermore, CS16 was embedded with sodium alginate and polyvinyl alcohol, and the capacities of CS16 to remove heavy metals after embedding were also determined.[Results] Agromyces sp. CS16 presented great metal removal capacity. For Cd²⁺, the strain showed the maximum removal capacity of 32.95 mg/g and the maximum removal rate of 83.71% with the initial Cd²⁺ concentration of 10 μg/mL. For Ni²⁺, Agromyces sp. CS16 presented the maximum removal capacity of 25.09 mg/g with the initial Ni²⁺ concentration of 75 μg/mL, and it presented the maximum removal rate of 70.27% with the initial Ni²⁺ concentration of 10 μg/mL. For Cu²⁺, CS16 had the maximum removal capacity of 30.69 mg/g with the initial Cu²⁺ concentration of 150 μg/mL and the maximun removal rate of 80.11% with the initial Cu²⁺ concentration of 30 μg/mL. For Zn²⁺, the strain had the maximum removal capacity of 39.29 mg/g with the initial Zn²⁺ concentration of 125 μg/mL and the maximun removal rate of 88.91% with the initial Zn²⁺ concentration of 25 μg/mL. A total of 3 744 genes were predicted in the whole genome of strain CS16, of which 37 genes were deduced to be associated with the resistance to Cd²⁺, Ni²⁺, Cu²⁺, and Zn²⁺. CS16 mainly removed heavy metals in water by adsorbing heavy metal ions on cell walls. The embedding with sodium alginate (SA) and polyvinyl alcohol (PVA) decreased the removal capacity of CS16 for Cd²⁺ and improved the removal capacities for Ni²⁺, Cu²⁺, and Zn²⁺. [Conclusion] Agromyces sp. CS16 is a new strain isolated from mangrove surface sediments, with great capacity in removing Cd²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ from water. We explored the metal removal mechanisms of the strain at both cellular and genetic levels. CS16 was embedded with sodium alginate and polyvinyl alcohol and the embedding product presented better removal capacity for Ni²⁺, Cu²⁺, and Zn²⁺. In summary, CS16 is an efficient microbial agent in bioremediation of heavy metal-polluted water. Moreover, the findings of this study provide a theoretical basis for deciphering the mechanism of removing heavy metal ions from water by microorganisms.