Characteristics of Pediococcus, Lactococcus, Leuconostoc, and Lactobacillus isolates and their bacteriocins

The objectives of this study are (1) to identify the bacteriocin-producing isolates to the species level, (2) to compare growth media for relative levels of bacteriocin production by the isolates, (3) to characterize the Bacteriocins for their molecular weight, host-range spectrum, and (4) to determine genetic linkage to plasmids. Eight Pediococcus, ten Lactococcus, six Leuconostoc, and four Lactobacillus isolates had been identified. They are Pediococcus acidilactici (7 strains), Pediococcus pentosaceus (one strain), Lactococcus lactis subsp. lactis (ten strains), Leuconostoc lactis (two strains), Leuconostoc carnosum (two strains), Leuconostoc mesenteroides subsp. mesenteroides (two strains), Lactobacillus collinoides (three strains), and Lactobacillus plantarum (one strain). Pediococcus isolates produced Bacteriocins in larger amount in TGE supplemented with Tween 80 than in other media. While Lactococcus and Lactobacillus isolates produced higher amount of Bacteriocins in TGE buffer supplemented with Tween 80, and MRS broth was found to be a suitable medium for bacteriocin production of Leuconostoc isolates. The molecular mass of Bacteriocins produced by Pediococcus and Lactococcus isolates are about 4.6 and 3.4 kDa, respectively. Bacteriocins produced by Leuconostoc isolates have molecular mass between 3.4 kDa and 4.6 kDa. However, the MALDI mass spectrometry analysis (only Bacteriocins produced by Leu. mesenteroides subsp. mesenteroides 9) indicated that the 30% isopropanol fraction of the HPLC-purified bacteriocin has a molecular weight of 3332 Da, while the 31% isopropanol fraction has a molecular weight of 4112 Da. Lab. plantarum BR4 has molecular mass about 4.3 kDa. All bacteriocins produced by all isolates are active against all strains of Listeria monocytogenes tested. However, none of them are active against Gram-negative bacteria. Bacteriocins produced by Lactococcus isolates have broader spectra of inhibition compared to bacteriocins produced by other isolates. Bacteriocins produced by Ped. acidilactici strains are encoded by a plasmid. Results showed that the plasmid size is similar with the plasmid that encodes pediocin AcH of Ped. acidilactici H, which is about 8.9 Kb. Leuconostoc isolates contain several plasmids, however the plasmid profiles of Bac- mutants are similar with that of Bac+ strains.