Antibacterial activity of peptides extracted from tryptic hydrolyzate of whey protein by nanofiltration

Ultrafiltration permeate of whey protein tryptic hydrolyzate was processed by nanofiltration (NF) to obtain retentate (NFR) and permeate (NFP) that were then tested as inhibitors of Listeria, Staphylococcus aureus and Escherichia coli. NFR at 20 mg mL^?1 was most effective as an inhibitor (P < 0.001); whereas E. coli was relatively resistant, the effect on Listeria and S. aureus was greater at 20 mg mL^?1 than at 10 mg mL^?1 (P < 0.01). Peptide analysis revealed that NFR was rich in anionic peptides over eight amino acid residues in length. The antibacterial activity of two anionic peptides (84–91 and 125–135) and a cationic peptide (36–42) derived from β-lactoglobulin was tested. Peptide 125–135 was more inhibitory (P < 0.05) than peptide 84–91 against Listeria monocytogenes and S. aureus; peptide 36–42 was not inhibitory. NFR appears to have potential as a natural bio-preservative.