Antimicrobial activity of lactic acid bacteria isolated from goat's milk and artisanal cheeses: characteristics of a bacteriocin produced by Lactobacillus curvatus IFPL 105.

A total of 203 lactic acid bacteria isolated from raw goat's milk and artisanal cheese were tested for antibacterial activity. Only two strains of Lactococcus lactis, one strain of Enterococcus faecalis and one strain of Lactobacillus curvatus were shown to produce a bacteriocin-like substance. Lactobacillus curvatus IFPL105 produced a heat-stable bacteriocin, which was hydrolysed by alpha-chymotrypsin, proteinase K and pancreatin and exhibited a broad spectrum of inhibitory activity. The bactericidal activity of the bacteriocin was more potent when sensitive strains were in the logarithmic growth phase, inducing cell lysis, as observed by decreases in optical density and release of intracellular marker enzymes. Curing experiments resulted in variants that lacked both bacteriocin activity and immunity to the bacteriocin. Plasmid profile analysis of the parental strain and the bacteriocin-negative variants indicated that a plasmid of about 46 kbp may be involved in bacteriocin production and immunity to this antibacterial compound.