investigation of antibacterial, acid and bile tolerance properties of lactobacilli isolated from koozeh cheese

lactobacillus strains are a major part of the probiotics, microflora of the intestine and of fermented dairy products, and are found in a variety of environments. the aim of this study was to find out the ability of bile and acid tolerance and antibacterial properties of the twenty eight isolates of three group lactobacilli namely lactobacillus plantarum, lactobacillus casei and lactobacillus delbruki. for this purpose twenty eight different lactobacillus strains that isolated from koozeh cheese as a traditional cheese were screened. the acid tolerance test was studied under ph 2.0 and 3.0 with 7.5 as control. the cell count for the acid tolerance test was obtained at an interval of 0, 1, 2 and 3 hours respectively and was pour plated on man, rogosa, and sharpe (mrs) agar to be incubated at 37 °c for 24 hours. all cells were selected for bile tolerance test in mrs broth containing bile concentrations of 0% as control and 0.3% as test. then cell counts were enumerated after 24 hours of incubation on mrs agar. results showed twenty seven isolates did not have ability to tolerate acid and bile salts and antimicrobial activity against four indicator bacteria included eshirichia coli, listeria monocytogenesis, bacillus cereus, salmonella entritidis. only one isolate namely lactobacillus casei could tolerate acid and bile salt and had antibacterial activity against of l. monocytogenesis. therefore we can consider this strain as a native probiotic but extra examinations was required.