The inhibitory activity of Lactic acid bacteria isolated from fresh cow cheese

Bakterije mliječne kiseline sastavni su dio prirodne mikroflore mlijeka, a produktima svog metabolizma mogu utjecati i na sigurnost mliječnih proizvoda. Njihovo antimikrobno djelovanje odvija se preko organskih kiselina, vodikovog peroksida, ugljičnog dioksida ili bakteriocina. Svrha ovog rada bila je utvrditi sastav populacije bakterija mliječne kiseline u svježim sirevima prikupljenim na zagrebačkim tržnicama, te istražiti njihov antimikrobni potencijal. Broj bakterija mliječne kiseline određivan je metodom ISO 1524:1998, biokemijska determinacija pomoću API 50 CHL, a inhibicijsko djelovanje prema Listeria monocytogenes NCTC 10527 agar difuzijskim testom. Broj bakterija mliječne kiseline u svježim sirevima (n=10) kretao se od 5,87 do 8,38 log10 CFU g-1. Biokemijskom determinacijom izolata (n=52) utvrđene su vrste Lactococcus lactis subsp. lactis (61,54 %), Lactobacillus helveticus (23,07 %), Leuconostoc mesenteroides subsp. cremoris (11,54 %) te Leuconostoc mesenteroides subsp. mesenteroides (3,85 %). Inhibicijsko djelovanje prema L. monocytogenes NCTC 10527 zabilježeno je u 18 izolata.Lactic acid bacteria are the constituent part of milk microbial flora that could influence the safety of dairy products due production of organic acids, hydrogen peroxide, carbon dioxide and bacteriocins. Taking this in consideration, the objective of this study was to investigate the composition of lactic acid bacteria population in fresh cow cheeses taken from local markets, as well as their antimicrobial capacity. Lactic acid bacteria counts were determined according to ISO 1524:1998 method, biochemical determination using API 50 CHL system, and inhibitory activity against L. monocytogenes NCTC 10527 by agar well diffusion assay. Lactic acid bacteria count in fresh cow cheeses (n=10) ranged from 5.87 to 8.38 log10 CFU g-1. Among 52 MRS isolates collected, 61.54 % were assigned to the Lactococcus lactis subsp. Lactis species, 23.07 % Lactobacillus helveticus, 11.54 % Leuconostoc mesenteroides subsp. cremoris and 3.85 % Leuconostoc mesenteroides subsp. mesenteroides. Antilisterial activity was found in 18 isolates