Isolation, characterization, and evaluation of probiotic properties of Lactic Acid bacteria from different fermented yoghurt drinks available in Bangladesh

Abstract

Lactobacillus spp. is the most commonly found probiotics strain in dairy products. In the present study, Lactobacillus spp. were isolated from four commercially available fermented yoghurt drinks, which were identified based on observing their morphological characteristics and through some biochemical tests such as, gram staining, MIU (Motility Indole Urease), catalase, citrate, TSI (Tripplr Sugar Iron), gas from glucose, milk coagulation activities, starch hydrolysis and bile esculin test.It was observed that isolated Lactobacillus spp. growth rate decreased with the increasing concentration of inhibitory substances like NaCl (2,4,8%) and phenol (0.1-0.8%). Additionally, good growth were observed in the presence of 2% NaCl and 0.1% phenol. The isolated Lactobacillus spp. did show good survival abilities in acidic (pH 2) and alkaline (pH 8) conditions, while their maximum growth was observed at pH 8.0. Isolated Lactobacilli were able to coagulate skim milk and produce gas from glucose.All of the isolates showed negative results in hemolytic activity, indicating that lactic acid bacteria are safe for use by humans. All isolates were evaluated for their antimicrobial activity against Staphylococcus aureus, Enterococcusspp, Bacillus spp, Escherichia coli, Salmonella typhi, Klebsiellaspp, Pseudomonas spp, Serratia spp, Candida albicans, Trichodermaresseii, Aspergillus spp. The majority of the isolates showed significant antimicrobial effectiveness against the targeted pathogens.Their susceptibility to selected eight antibiotics was determined in terms of zone of inhibition (mm). In conclusion, most of the results from the present experiments showed that, there were very few variations in probiotics properties of the isolated Lactobacillus spp. from different fermented yoghurt drinks.