Synergistic effect between different milk-derived peptides and proteins.

Antimicrobial peptides derived from food proteins constitute a new field in the combined use of antimicrobial agents in food. The best examples of milk-derived peptides are those constituted by bovine lactoferricin [lactoferrin f(17-41)] (LFcin-B) and bovine alpha(s2)-casein f(183-207). The aim of this work was to study if the antimicrobial activity of a natural compound employed in food preservation, nisin, could be enhanced by combination with the aforementioned milk-derived peptides. Furthermore, the possibility of a synergistic effect between these peptides and bovine lactoferrin (LF) against Escherichia coli and Staphylococcus epidermidis was also studied. Finally, the most active combinations were assayed against the foodborne pathogens Listeria monocytogenes and Salmonella choleraesuis. Results showed a synergistic effect when LFcin-B was combined with bovine LF against E. coli. In the same way, the combination of LFcin-B with bovine LF was synergistic against Staph. epidermidis. Bovine LF and nisin increased their antimicrobial activity when they were assayed together with bovine alpha(s2)-casein f(183-207). It is important to note the synergistic effect among LFcin-B and bovine LF, because both compounds might be simultaneously in the suckling gastrointestinal tract and could, therefore, have a protective effect on it. The other synergistic effect high-lighted is that between alpha(s2)-casein f(183-207) and nisin against L. monocytogenes because of the ability of L. monocytogenes to develop resistance to nisin.