Characterization of Lactococcus species isolated from traditionally produced cheese

Autohtono prisutna mikrobiota u tradicionalno proizvedenim fermentiranim proizvodima odgovorna je za biokonzerviranje i senzorska svojstva proizvoda. Stoga je iz tradicionalno proizvedenih sireva provedena izolacija autohtonih bakterija mliječne kiseline (BMK) s ciljem odabira predstavnika Lactococcus vrsta kao potencijalnih probiotičkih starter kultura. Odabrani autohtoni izolati su pomoću klasičnih mikrobioloških metoda okarakterizirani kao gram-pozitivni, katalaza-negativni, nesporogeni, kuglasti, koji uspješno spuštaju pH vrijednost hranjive podloge, te sintetiziraju visoke koncentracije mliječne kiseline. Provedena je genotipska identifikacija sekvencioniranjem 16S rRNA gena prema kojoj je među odabranim autohtonim BMK bilo prisutno 24 različitih bakterijskih sojeva iz roda Lactococcus. Autohtoni sojevi BGAL1-1, BGLE1-6, ZG5-9 najbolje preživljavaju simulirane uvjete gastrointestinalnog trakta. Ispitivana je osjetljivost Lactococcus vrsta na 12 različitih antibiotika, te je utvrđeno da je soj Lactococcus lactis ZG2-11 rezistentan na neomicin, dok su bakterije Lactococcus lactis subsp. lactis BGAL1-4, Lactococcus lactis ZG1-51, Lactococcus lactis ZG2-11, te Lactococcus garviae BGRE2-21 rezistentne na streptomicin. Bakterija Lactococcus lactis ZG4-2 pokazala je rezistenciju na penicilin. Ostali ispitivani izolati osjetljivi su na sve korištene antibiotike.Autochtonous microbiota contribute to the biopreservation and sensory properties of traditional fermented food products. Therefore, isolation of the autochthonous isolates of lactic acid bacteria (LAB) from traditionally produced cheeses was performed aimed to select representatives of Lactococcus species with a potential as probiotic starter cultures. Selected autochthonous isolates were characterized as gram-positive, catalase-negative sphere-shaped bacteria by conventional microbiological methods, which were successfull in lowering pH value of the medium and synthesized high concentrations of lactic acid. Identification performed by 16S rRNA gene sequencing revealed that between selected autochthonous LAB 24 different strains were identified as representatives of Lactococcus. Autochthonous LAB BGAL1-1, BGLE1-6 and ZG5-9 showed high survival rates in simulated gastrointestinal tract conditions. Investigation of the susceptibility to different antibiotics revealed that Lactococcus lactis ZG2-11 was resistant to neomycin while strains Lactococcus lactis subsp. lactis BGAL1-4, Lactococcus lactis ZG1-51, Lactococcus lactis ZG2-11, and Lactococcus garviae BGRE2-21 were resistant to streptomycin. Lactococcus lactis ZG4-2 showed a resistance to penicillin. Other isolates were sensitive to all antibiotics used