E. coli surface-displayed nickel-binding peptides for preferential nickel recovery from battery wastewater:...

In this study, engineered E. coli BL21(DE3) strains were constructed to display nickel-binding peptides (NBPs) on the surface via fusion to the outer membrane protein OmpC. Four NBPs were evaluated for nickel adsorption and metal-ion selectivity, using a combination of computational predictions and experimental validation. Computational analyses predicted peptide structure, localization, electrochemical properties, and Ni²⁺ binding sites. Among the tested NBPs, NBP4 exhibited the highest nickel adsorption and selectivity (Ni > Co > Mn > Li) across the evaluated concentration range. In real battery wastewater, all strains effectively removed nickel, with NBP4 achieving the highest removal rate (90%), followed by NBP1, NBP2, and NBP3. Reuse of NBP4-displaying cells decreased the adsorption efficiency from 90% to 22% over five cycles. Field emission scanning electron microscopy (FE-SEM) and energy-dispersive spectroscopy (EDS) analysis confirmed nickel adsorption on the cell surface. Calcination of metal-bound cells yielded crystalline, cubic nickel oxide (NiO) nanoparticles measuring 400-600 nm, as verified by X-ray diffraction (XRD), FE-SEM, and Nano Zeta sizer analyses. These findings demonstrate that peptide-displaying bacterial systems have significant potential to adsorb and recover nickel from industrial effluents.