Isolation, Identification and Analysis of Probiotic Properties of Lactobacillus Spp. from Selective Regional Yoghurts

Abstract

Yoghurt is a potential source of probiotic lactobacilli. In the present study, Lactobacillus spp. were isolated from two regional yoghurts of Bangladesh, which were identified on the basis of their colony morphologies and biochemical assays. It was observed that isolated Lactobacillus spp. were resistant to inhibitory substances like phenol (0.4%), NaCl (1-9%) and bile acid (0.05-0.3%). Additionally, their good growth was observed in the presence of 1% NaCl and 0.3% bile acid. The isolated Lactobacillus spp. did show good survival abilities in acidic (pH 2.5) and alkaline (pH 8.5) conditions, while their maximum growth was observed at pH 5.0 in case of lactobacilli isolated from Bogra yoghurt and at pH 6.5 in case of lactobacilli isolated from yoghurt of Khulna region of Bangladesh. Isolated lactobacilli were able to produce organic acid in the skim milk which was determined by titrimetric method. The Lactobacillus spp. also did show good survival abilities in simulated gastric juice at pH 2.22 and pH 6.6 (control). Their susceptibility to selected nine antibiotics was determined in terms of minimum inhibition concentration (MIC). The MICs results showed that, Lactobacillus spp. isolated from Bogra yoghurt were sensitive to amoxicillin, moderately sensitive to gentamycin, clindamycin, azithromycin and resistant to kanamycin, nalidixic acid, metronidazole, cefradine and tetracycline. On the other hand, Lactobacillus spp. isolated from yoghurt of Khulna region of Bangladesh were sensitive to gentamicin, clindamycin and resistant to amoxicillin, tetracycline, kanamycin, nalidixic acid, metronidazole, azithromycin and cefradine. Observations from the present communications show that, there were variations in probiotic properties of the isolated Lactobacillus spp. from regional yoghurts. Therefore, species level isolation, identification and probiotic properties of regional lactobacilli need to be studied.