Determination of probiotic potential of lactic acid bacteria (LAB) isolated from different origins

Probiotics are beneficial microorganisms that show survival under gastrointestinal conditions, adhesion to the intestinal surface and different functions which result in several health benefits to the host. With this regards, this study aimed to isolate LAB from sourdough and human feces and test their potential probiotic functions. At first, the genes responsible for the EPS production were detected by PCR analysis. Then the level of EPS production was determined by DNS analysis and the monomer composition of the EPS structure was determined by HPLC analysis and in all EPSs from distinct strains glucose was detected. In antibiotic sensitivity tests, while all isolates were resistant to kanamycin, all isolates were resistant to streptomycine, except L. rhamnosus C-9A and P. pentosaceus WPS-8 strains. In general, antimicrobial activity was observed against tested pathogens except L.rhamnosus C-9A and L.paracasei WPS-11 which did not reveal any antimicrobial activity against Salmonella typhimurium. The antifungal activity of the isolates was determined against 6 fungi and all strains revealed different level of antifungal activity. The cell surface hydrophobicity was determined with n-hexadecene and strains revealed % 3-81.2 level of hydrophobicity and P.pentosaceus WPS-8 showed the highest hydrophobicity. Importantly, the adhesion to HT29 cells was determined and the adhesion levels were determined between %0.29-9.54 and L.paracasei C-7B showed the highest adhesion. In general all isolates tolerated the bile salt after 24 h and the sourdough isolates showed lower level of survival at pH 4. Similarly, the survival under simulated gastrointestinal conditions of the isolates was determined to be between %39-97. Production of GABA among the LAB isolates was also determined as an important compound for neural system. In conclusion, tested isolates from sourdough and human feces could be potential probiotic strains.