Characterization of lactic acid bacteria of the genus Lactobacillus and Bifidobacterium present in the lyophilized probiotic preparations

U ovom radu provedeno je ispitivanje fizioloških i funkcionalnih svojstava bakterija iz rodova Lactobacillus i Bifidobacterium prisutnih u liofiliziranim probiotičkim pripravcima. Bakterijski sojevi izolirani su iz uzoraka probiotičkih pripravaka korištenjem selektivnih hranjivih podloga. Fenotipska karakterizacija izoliranih sojeva provedena je odabirom gram-pozitivnih, nesporogenih, katalaza-negativnih bakterija, uz analizu fermentacijskih profila šećera za bakterije roda Lactobacillus standardiziranim biokemijskim testovima metabolizma ugljikohidrata i ostalih supstrata pomoću API 50 CHL testa. Nakon fenotipske karakterizacije definirana je i funkcionalnost ovih sojeva analizom najvažnijih probiotičkih kriterija. Tijekom izlaganja simuliranim uvjetima gastrointetsinalnog trakta broj živih stanica svih ispitanih sojeva, osim sojeva Bifidobacterium sp. 3, Bifidobacterium sp. 2B i Bifidobacterium sp. 6B se održao iznad 106 CFU/ml, pri čemu je najbolje preživljavanje pokazao soj Lactobacillus sp. 7A čiji se broj živih stanica smanjio za samo 0,94 log jedinica. Svi ispitani sojevi pokazuju autoagregacijska svojstva. Bakterijski sojevi Lactobacillus sp. 7A i Lactobacillus sp. 2A u najvećem postotku koagregiraju sa stanicama Escherichia coli 3014 (cca 55%), bakterijski sojevi Lactobacillus sp. 1, Lactobacillus sp. 8/1 i Bifidobacterium sp. 8/2 koagregiraju oko 40%, dok sojevi Lactobacillus sp. 1, Lactobacillus sp. 2A i Lactobacillus sp. 7A u najvećem postotku koagregiraju s bakterijom Salmonella enterica serovar Typhimurium FP1 (oko 50%) te Lactobacillus sp. 8/1 oko 30%. Visoki postotak adhezije stanica sojeva Bifidobacterium sp. 3, Lactobacillus sp. 8/1 i Bifidobacterium sp. 8/2 na heksan upućuje na njihovu hidrofobnost, a afinitet svih ispitivanih sojeva za kloroform, na elektron-donorska svojstva površine bakterijskih stanica. Svi sojevi pokazuju slabu aktivnost hidrolaze žučnih soli jer su dekonjugirali 10-15% taurokolata dodanog u hranjivu podlogu.This work was carried out in order to characterise physiological and functional properties of bacteria from the Lactobacillus and Bifidobacterium genera, which are present in the freeze-dried probiotic formulations. Bacterial strains were isolated from different commercially available probiotic supplements using selective media isolation. Phenotypic characterization of the isolates was performed by selection of the gram-positive, non-sporogenic, catalase-negative bacteria and analysis of fermentation profiles of Lactobacillus bacteria with standardized biochemical tests of carbohydrate metabolism and other substrates using API 50 CHL test. After the phenotypic characterization of isolated bacterial strains, the functionality of these strains is defined by analysis of the most important probiotic criteria. During exposure to simulated gastrointestinal tract conditions, the number of viable cells of all tested strains, except strains Bifidobacterium sp. 3, Bifidobacterium sp. 2B and Bifidobacterium sp. 6B was held above 106 CFU/ml, where strain Lactobacillus sp. 7A showed the best viability, which number of viable cell count decreased by only 0,94 log units. All tested strains showed good auto-aggregate properties and bacterial strains Lactobacillus sp. 7A and Lactobacillus sp. 2A co-aggregated with the largest percentage with Escherichia coli 3014 (approx 55%), Lactobacillus sp. 1, Lactobacillus sp. 8/1 i Bifidobacterium sp. 8/2 co-aggregated approx 40%, while strains Lactobacillus sp. 1, Lactobacillus sp. 2A and Lactobacillus sp. 7A co-aggregated the best with Salmonella enterica serovar Typhimurium FP1 (approx 50%) and Lactobacillus sp. 8/1 co-aggregated approx 30%. High percentage of cell adhesion of strains Bifidobacterium sp. 3, Lactobacillus sp. 8/1 and Bifidobacterium sp. 8/2 to the hexane indicates their hydrophobicity, and the affinity of all tested strains of chloroform, to the electron-donor properties of the surface of bacterial cells. All strains showed weak activity hydrolase bile salts because they are deconjugate only 10-15% taurocholate added in the culture medium