A novel bioengineered strategy for efficient heavy metals remediation: Harnessing alkaline phosphatase-displaying E....

Microbial-induced phosphate precipitation (MIPP) is a promising strategy for heavy metal removal, but its practical application is often hindered by low extracellular phosphatase activity and inefficient metal sequestration. To address this, engineered Escherichia coli strains that display alkaline phosphatase on its outer membrane via fusion with OprF and YiaT anchoring motifs were developed. The resulting whole-cell biocatalyst exhibited high alkaline phosphatase activity (75 U mL^-1) and exceptional heavy metal removal capabilities, particularly for Pb²⁺, Cd²⁺, and Mn²⁺, with efficiencies exceeding 98 %. Kinetic analysis revealed the biomineralization process follows pseudo-second-order kinetics, indicating a chemisorption-dominated process. The heavy metal removal mechanism was further explored using the techniques of SEM, TEM, FT-IR and XRD. Results demonstrate that surface-displayed alkaline phosphatase mediates extracellular phosphate precipitation with metals, forming distinct mineral morphologies, while partial intracellular translocation occurs. Specifically, Co²⁺ precipitated as stable Co₃(PO₄)₂·8H₂O. This work advances MIPP technology through engineered alkaline phosphatase display, offering a scalable and efficient solution for sustainable heavy metal remediation.