Isolation of lactococcus lactis strains producing inhibitory activity against listeria

Abstract

Summary

Fifty‐one bacteriocin‐producing bacteria (Bac⁺) were isolated from 35 raw milk cheeses by the deferred antagonism method using Listeria strains as indicator organisms. Of the 51 Bac⁺ isolates, 10 that were identified as Lactococcus lactis subsp. lactis by biochemical and physiological tests, and were selected on the basis of the inhibition zone diameter (>10 mm). Five lactococcal strains containing the nisA or nisZ genes, the structural genes for nisin biosynthesis, were selected with specific PCR amplifications, and the other five isolates were shown to produce a bacteriocin different from nisin. Seven of the ten isolates including two presumptive nisogenic strains, showed good capacity for milk acidification decreasing the pH of milk from 6.5 to 4.7–4.3.

Notes

corresponding author