Ureolytic Rhizobacteria for Cadmium Remediation: Contribution of Bioadsorption and Bioaccumulation During Microbially Induced Carbonate Precipitation in Liquid Medium Assays
TL;DR
Comparative analysis of Cd bioprecipitation and biosorption assays, combined with sequential extraction, demonstrated that bioadsorption plays a significant role in the removal of Cd via MICP, highlighting the need to evaluate removal mechanisms when assessing bacterial MICP potential.
Abstract
Microbially induced carbonate precipitation (MICP) is a recognized bioremediation strategy for mitigating toxic metal pollution; however, the relative contributions of bioprecipitation, biosorption, and bioaccumulation to cadmium (Cd) removal during MICP remain underexplored. This study assessed Cd immobilization by six rhizosphere ureolytic bacterial strains from different genera in liquid medium and quantified the metal distributed among the bioprecipitated, biosorbed, and bioaccumulated fractions. Minimum inhibitory concentration assays showed Cd tolerance ranging from 90 to 300 mg L−1. The strains presented total Cd removal efficiencies of 64.9%–99.8% within 120 h. Notably, Cd removal occurs mainly under 48 h. Biosorption assays revealed substantially lower Cd removal compared with bioprecipitation experiments. Comparative analysis of Cd bioprecipitation and biosorption assays, combined with sequential extraction, demonstrated that bioadsorption plays a significant role in the removal of Cd via MICP. Precipitates characterization further confirmed coprecipitation of Cd with vaterite, a calcium carbonate polymorph. These findings elucidate an important role of biosorption in Cd immobilization during MICP, highlighting the need to evaluate removal mechanisms when assessing bacterial MICP potential, as different mechanisms can lead to distinct long‐term stability outcomes.