Evaluation of probiotic properties of lactobacilli Isolated from coagulated cow's milk

The aim of this study was to investigate the probiotic characteristics of the isolated lactic acid bacteria (LAB) in coagulated cow's milk including antimicrobial activities, acid and bile tolerance, fermentation profile, hemolytic properties, acidification and coagulation collected from some villages of Tehran province were examined. Among the 13 milk samples collected, 7 isolates were identified as lactic acid bacteria based on phenotypic and biochemical tests. In order to determine the biochemical results, their DNA was extracted and amplified by PCR with specific primer and then sequenced by PCR products and they were recorded in the NCBI database. These results definitely confirmed that the isolated strains belong to lactobacilli. The results showed all isolated LABs were positive for hemolytic activity. LABs A and C showed beta hemolysis. LAB E showed the highest resistance to acidic environments, whereas all the our isolates were resistant to bile conditions. The supernatant obtained from lactic acid bacteria had an effect on Escherichia coli and a non-growth halo was created. But it had no effect on staph and fungi. all LAB isolates exhibited the ability of acid production and coagulation at 30°C. In contrast, none of the LAB isolates presented coagulation potential at 30 °C. Based on this study results, LAB E and C isolated from coagulated cow's milk could be considered as probiotic microorganisms considering the observed properties. They can be purified and used for the production of probiotic dairy products.