QUALITATIVE ANALYSIS OF LACTOBACILLUSSTRAINS IN MILK PROBIOTICS

In the present study, an attempt was taken for qualitative analysis (to detect the presence) of Lactobacillusstrains: one of the major bacterial strains of milk probiotics by different biochemical tests, salt & pH tolerance and subsequently sugar & casein fermentation tests of cheese, curd and milk kefir.Gram staining and colony morphology of each isolated bacterial colony primarily indicated the presence of Lactobacillus species which was further confirmed by different biochemical and selective tests for Lactobacillus species. Negative catalase test as well as positive Kilger?s iron agar, oxidase and Simon citrate as biochemical tests confirmed the presence of Lactobacillus species in the test samples. Additionally, good to moderate sugar (sucrose, fructose, glucose & lactose) and skim milk fermentation revealing deep red color and clear zone appeared around the areas in the medium where the organism had grown, proved the presence of Lactobacillus species in the samples. Moreover, less growth or absence of bacteria in MRS broth medium containing higher salt concentration (8% NaCl solution and above) and having higher pH value by adding 1N HCl (pH 3 and above) finally confirmed that cheese, curd and milk kefircontain Lactobacillus species.