Probiotic Properties of Lactic Acid Bacteria Isolated from Croatian Fresh Soft Cheese and Serbian White Pickled Cheese

Svrha je ovog rada bila istražiti probiotički potencijal autohtonih bakterija mliječne kiseline (BMK), izoliranih iz tradicionalnog svježeg sira i bijelog sira u salamuri. Od 86 je izolata BMK iz tradicionalno proizvedenih svježih sireva i bijelih sireva u salamuri odabrano njih 11, koji su preživjeli simulirane uvjete gastrointestinalnog trakta i nisu pokazali rezistenciju na antibiotike. Ti su sojevi uključeni u daljnju procjenu funkcionalnih probiotičkih svojstava. Asimilacija kolesterola u prisutnosti žučnih soli razlikovala se za pojedine ispitivane sojeve, a najveći je postotak asimiliranog kolesterola postignut uporabom soja Lactobacillus brevis BGGO7-28, koji na površini stanica ima sloj S-proteina. Bolji rast odabranih sojeva BMK postignut je u prisutnosti prebiotičkih supstrata manitola i laktuloze, u usporedbi s rastom u prisutnosti fruktooligosaharida (FOS) i inulina, koji su bili jedini izvori ugljika u hranjivoj podlozi, što treba uzeti u obzir pri formulaciji sinbiotičkih pripravaka. Osim toga, ustanovljen je veći adhezijski afinitet ispitivanih sojeva za humanu staničnu liniju crijevnih epitelnih stanica Caco-2, nego staničnu liniju HT29-MTX, s izuzetkom soja L. brevis BGGO7-28, s kojim je postignut podjednak postotak adhezije na obje ispitivane stanične linije. Isti je bakterijski soj jedini imao elektron-akceptorska svojstva površine stanica, dok su kod preostalih ispitivanih sojeva prevladavala elektron-donorska svojstva. Nadalje, svi su odabrani sojevi inhibirali proliferaciju stanica limfatičnog tkiva probavnog sustava (engl. gut-associated lymphoid tissue, GALT), što upućuje na zaključak da ispitani izolati BMK imaju imunomodulacijski potencijal. Nakon liofilizacije odabranih sojeva broj se živih stanica u suhim aktivnim pripravcima razlikovao ovisno o primjenjenom lioprotektoru (inulin, FOS ili obrano mlijeko). Na osnovi se dobivenih rezultata može zaključiti da ispitivani izolati BMK imaju probiotička svojstva specifična za svaki pojedini soj. Stoga će se dodatno istražiti kao sastavni dio mješovitih autohtonih starter kultura za proizvodnju tradicionalnih sireva u kontroliranim uvjetima.The aim of this study is to gain insight into the probiotic potential of autochthonous lactic acid bacteria (LAB) isolated from artisanal fresh soft and white pickled cheeses. Eleven out of 86 LAB isolates from traditionally produced artisanal fresh soft and white pickled cheeses which survived the most rigorous simulated gastrointestinal tract conditions and did not show resistance to antibiotics were subjected to further evaluation for functional probiotic properties. The ability of the examined strains to assimilate cholesterol in the presence of bile salts was strain dependent, with the highest percentage of cholesterol assimilated by strain Lactobacillus brevis BGGO7-28 possessing S-layer proteins on its cell surface. The growth of strains with mannitol or lactulose as the only carbon source was better than with fructooligosaccharides (FOS) and inulin as prebiotic substrates, which should be considered in the production of synbiotics. Moreover, the results demonstrated that the strains were highly adhesive to human enterocyte-like Caco-2 cells and to a lesser extent to HT29-MTX cells, with the exception of strain Lb. brevis BGGO7-28, which showed similar percentage of adhesion to both cell lines. This strain was the only one with the acidic cell surface, while other examined strains have the cell surfaces with electron donor and basic properties. In addition, all selected strains decreased the proliferation of gut-associated lymphoid tissue (GALT) cells, suggesting possible immunomodulatory potential of the isolates. Finally, the number of viable cells in dry active preparations after lyophilisation depended on the lyoprotectant used (inulin, FOS or skimmed milk), as well as on the strain subjected to lyophilisation. In conclusion, the results obtained in this study demonstrate that particular dairy LAB isolates exhibit strain-specific probiotic properties. Thus, they could be further examined as part of mixed autochthonous starter cultures for traditional cheese production under controlled conditions