Functionalized bacteria used as adsorbents for uranium extraction from seawater

Abstract

Selective extraction of uranium from seawater remains challenging due to its ultra-low concentration and the presence of competing ions. In this study, an engineered bacterial biosorbent (BDU09) was constructed by displaying the uranium-binding protein U09 on the outer membrane of Escherichia coli EcN 1917 via the Lpp-OmpA surface display system. To enhance mechanical stability and enable practical application, BDU09 cells were encapsulated within polyethylene glycol diacrylate (PEGDA), forming structurally stable microbial beads with high selectivity toward U(VI). Batch adsorption experiments demonstrated that both BDU09 and the corresponding microbial beads exhibited selective U(VI) uptake in the presence of competing ions, driven by specific coordination interactions between U(VI) and surface functional groups. The microbial beads maintained favorable selectivity and structural integrity in uranium-spiked simulated seawater as well as natural seawater. Continuous fixed-bed column experiments further confirmed effective U(VI) separation, with breakthrough behavior significantly influenced by initial concentration, bed height, and flow rate. The adsorption process was well described by the Yoon–Nelson model, and high-purity U(VI) recovery was achieved in simulated seawater. This work translates protein-level binding specificity into a mechanically robust and scalable biosorption platform, offering a promising strategy for uranium extraction from seawater.