An anti-listerial Lactococcus lactis strain isolated from Azorean Pico cheese produces lacticin 481

Abstract

A bacteriocin produced by a strain of Lactococcus lactis (L3A21M1), isolated from an Azorean cheese, was purified, characterised and identified. This bacteriocin, of molecular mass 2900.23 Da, similar to that of lacticin 481, was heat stable, active across a wide pH range and exhibited a broad spectrum of activity. It revealed a bacteriostatic mode of action against Listeria monocytogenes both in culture media and in model cheeses. Also, the strain presented good auto-aggregation, as well as co-aggregation ability with L. monocytogenes. The strain cell surface was relatively hydrophobic and basic, presented low tolerance to acidic conditions, but good resistance to the gut environment. The strain was able to reduce the adhesion of L. monocytogenes to Caco-2 and HT-29 cells in competition, displacement, inhibition and invasion experiments. The Lc. lactis L3A21M1 strain therefore has significant anti-listerial activity and so may find application for both food protection and decreased risk of infection.