Phage display screening for highly specific nickel- and cobalt-binding peptides for bio-recovery of metals

Electronic waste is a valuable source of critical metals like nickel and cobalt, but their recovery is challenging. Current recycling processes use harsh conditions and toxic chemicals, which is why environmentally friendly alternatives are crucial. Metal-binding peptides offer high selectivity and durability, making them promising for sustainable metal separation. Here, phage display was successfully applied to screen a combinatorial peptide library with specific affinities to nickel or cobalt. Identified peptides with the amino acid sequences FWPLHHH, GPHKHHA, HNYHHRH, and HMNHHHH revealed improved binding affinities of up to 20.000-fold to immobilized metal ions compared to the unspecific binding of the phage backbone. Furthermore, low micromolar dissociation constants e.g., 6.2 µM for peptide Co_02 (HMNHHHH) to Co²⁺ and 29.0 µM for peptide Ni_01 (GPHKHHA) to Ni²⁺, determined by Isothermal Titration Calorimetry (ITC) measurements confirmed the intrinsic metal binding properties. These peptides offer a high potential for future recycling of nickel and cobalt from mixed metal waste like batteries.