Antibacterial activity of three Leuconostoc strains isolated from vacuum-packaged processed meats

One hundred and fifty lactic acid bacteria (LAB) isolated from vacuum-packaged processed meats were screened for antagonistic activity against various food spoilage microorganisms and foodborne pathogens. Nineteen strains produced bacteriocins active against closely related LAB and Listeria strains. Leuconostoc carnosum (LA54a and TA26b) and Leuconostoc mesenteroides subspecies dextranicum (TA33a) produced bacteriocins that were susceptible to proteolytic enzymes, but not to catalase, lysozyme or chloroform. They were heat stable up to 100 degrees C for thirty minutes at pH 2 to 7, and exerted a bacteriolytic effect. Bacteriocin production by all Leuconostoc strains was growth associated, occurring at incubation temperatures of 0 degrees C to 30 degrees C and initial medium pH 4.5 to 7.5. Probing of plasmid DNA from the three Leuconostoc strains with an oligonucleotide probe homologous to the nucleotide sequence of leucocin A-UAL 187 indicated plasmid-mediated bacteriocin production. Homology of the three Leuconostoc bacteriocin-coding genes to the amino-terminal end of the leucocin A-UAL 187 gene from Leuconostoc gelidum UAL 187 is therefore suggested. This evidence implies that all three Leuconostoc strains produce type 2, Listeria active bacteriocins.