Isolation and characterisation of zinc-chelating peptides from tilapia ( <i>Oreochromis niloticus</i> ) protein hydrolysate

Abstract This study aimed to isolate and characterise zinc-chelating peptides from tilapia (Oreochromis niloticus) protein hydrolysate. The hydrolysate was fractionated using a multi-ultrafiltration technique, yielding peptide fractions with molecular weights between 0.5 and 5 kDa. These fractions were further purified using immobilised metal ion affinity chromatography (IMAC-Zn2+) and reverse high-performance liquid chromatography (RP-HPLC). Among the fractions obtained, the peptide fraction F211 exhibited a zinc-binding capacity of 76.26 ± 2.46 mg g−1. Sequence analysis indicated that zinc binding occurred at amino acids on the F21 peptide and at valine or glutamate residues on the F22 peptide fraction. Structural characterisation revealed that amino nitrogen and oxygen atoms from carboxylate groups were the primary binding sites for Zn2+. Additionally, the zinc–peptide complex demonstrated strong thermal stability, which is significant for potential applications in food processing and storage, where maintaining the integrity of nutritional supplements under varying temperature conditions is crucial. These findings provide a feasible approach for the separation and purification of zinc-binding peptides from tilapia protein hydrolysates and contribute to the understanding of the binding mechanisms between zinc and peptides.