Work

Removal of high concentrations of zinc, cadmium, and nickel heavy metals by Bacillus and Comamonas through microbially induced carbonate precipitation

Year: 2025

Type: article

Abstract: Heavy metal pollution in urban freshwater, driven by anthropogenic activities, poses significant risks to aquatic ecosystems and human health due to its toxicity and persistence. Recently, urease-producing bacteria have gained attention for their ability to remove heavy metals through microbial-induced carbonate precipitation (MICP). In this study, eight urease-producing bacteria were exposed to individual solutions of zinc (Zn 2+ ), cadmium (Cd 2+ ), and nickel (Ni 2+ ) at concentrations ranging from 0 to 6 mM to assess their resistance. Three strains— Bacillus subtilis HMZC1 (B2), Bacillus sp. HMZCSW (B6), and Comamonas sp. HMZC (B11)—survived at 4 mM and 6 mM, while most others could not tolerate 4 mM. Their urea-degrading ability was tested at different pH levels, identifying an optimal pH of 7 for MICP. Heavy metal carbonate precipitation experiments at 4 mM and 6 mM revealed that all three strains achieved > 93% removal of Zn 2+ , Ni 2+ , and Cd 2+ within 72 h. Comamonas sp. HMZC exhibited the highest efficiency, achieving > 95% removal of certain heavy metals at 6 mM. Statistical analysis using one-way ANOVA revealed significant differences (p < 0.05) in heavy metal removal efficiencies among the strains for certain treatment conditions (Cd 2+ and Zn 2+ at 4 mM), although not all comparisons reached statistical significance. Scanning Electron Microscopy and X-ray Diffraction confirmed the morphology and composition of the precipitated heavy metal carbonates. Our findings demonstrate that urease-producing bacteria can effectively immobilize multiple heavy metals, highlighting the MICP process as a practical and sustainable biological approach for ecological restoration and wastewater treatment.

Source: Biodegradation

DOI: 10.1007/s10532-025-10131-7