Bioremediation of Sr2+ contamination based on microbially induced carbonate precipitation (MICP) simulated by Enterobacter sp.

Abstract

Microbially induced carbonate precipitation (MICP) has shown significant potential for Sr²⁺ bioremediation in both laboratory and field settings. However, previous studies have primarily focused on urease-producing bacteria, with the potential of ammonifying bacteria remaining largely uninvestigated. This study explores the capacity of the ammonifying bacterium Enterobacter sp. JC-1 to promote carbonate mineral formation and enhance Sr²⁺ removal under both static and shaking conditions. Solution chemistry analysis indicated that Enterobacter sp. JC-1 strain elevated both the pH value and HCO₃^- concentration, inducing supersaturation with respect to calcite and strontianite, thereby promoting carbonate precipitation. Mineralogical characterization via XRD and SEM confirmed the formation of calcium-bearing strontianite with a microspherical morphology. During mineralization, Sr²⁺ and Ca²⁺ co-precipitated at molar ratios of approximately 1:1 (static conditions) and < 1:1 (shaking conditions), achieving Sr²⁺ removal rate of 22 % and 33 %. Correlation analysis identified OD₆₀₀ and mineral mass as key factors influencing Sr²⁺ removal. Comparative analysis with previous studies indicated that the Sr²⁺ removal rate of JC-1 strain was lower than that of urease-producing bacteria, it exceeded that of urease-producing fungi. These findings highlight the potential of ammonifying bacteria as viable candidates for MICP-based bioremediation of heavy metals and radionuclides, thereby expanding the applicability of MICP in environmental engineering.