Isolation, identification and investigation of probiotic properties of lactic acid bacteria isolated from local yogurts of Bonab city

The importance of probiotics in balancing the microbiota, regulating the function of the immune system, preventing the occurrence and recurrence of infectious diseases, improving digestive disorders and many other benefits has been proven. Investigations in traditional and local fermented products have led to the isolation of lactic acid bacteria in the genera Lactobacillus, Bifidobacterium and Streptococcus, which are usually considered as probiotics. In this study, three local cow yogurts from Bonab city were used to isolate probiotics. Probiotic properties including tolerance to simulated digestive system conditions such as acid resistance, bile salt resistance, hydrolysis of cholesterol and bile salts, antimicrobial properties and physiological tests such as hydrophobicity, auto-aggregation and co-aggregation were investigated and finally selected isolates were evaluated for molecular identification. Of these three traditional products, 11 isolates were investigated, of which 7 isolates belonged to Lactobacilli and 4 isolates belonged to Streptococci. Most of the isolates were probiotic candidates in two or three characteristics, but among them, 2 isolates had better results in most of the probiotics evaluation tests using PCR for the16S rRNA gene analysis.The tests confirmed that both isolates were Lactobacilli. After sequencing and blasting the sequences on the NCBI site, it was found that one isolate is Lactobacillus casei and the other is Lactobacillus rhamnosus with more than 99% similarity. This study confirms that traditional dairy products are important sources for the isolation of probiotic bacteria. Therefore, the identification and optimization of local isolates, which in most studies have better probiotic potential, can pave the way for the production of probiotic supplements.