ISOLATION AND CHARACTERIZATION OF PROBIOTIC LACTOBACILLUS SPECIES FROM CURD SAMPLES AND EVALUATION OF THEIR ANTAGONISTIC POTENTIAL

摘要

Fermentative milk products with probiotic properties escalate as a necessary substitution in human and animal feed consumption for well being of the gut microflora. One of the key aspects is being the reducing the population of pathogens and production of vitamins. The live bacterial community of these fermented foods can reduce the effect of antibiotics and increase the immune function. Ten beneficial Lactobacillus sp. were isolated from two local curd samples and characterized in terms of morphological, biochemical, molecular and physiological characteristics. Antagonistic potential of all the isolates were studied against enteric pathogens; Escherichia coli, Salmonella typhi, Shigella boydii and Enterococcus faecalis. All are gram-positive rod of non-endospore forming ability with pH tolerance range of 5-8, NaCl tolerance limit of 5% (w/v). A wide spectrum of antibiotic resistance was noticed for all the isolates. Almost all isolates showed antagonism against E. coli and S. typhi followed by S. boydii and E. faecalis and strains OC3 and KC2 were found to be the best potential candidates. Bacteriocin extract showed a little difference denoting OC3 and KC2 as well as OC5 as effective against all the enteric pathogens. 16S rRNA gene sequence analysis and phylogenetic characterization revealed the taxonomic affiliation of the strain OC3 and KC2 to L. brevis ATCC 14869 (T) and L. paraplantarum DSM 10667 (T) showing 99% of sequence similarity with high phylogenetic lineage towards probiotic Lactobacillus type strains. These strains can be used as potential probiotic agents as starter inoculum for the fermented foods and reducing disease incidence caused by enteric pathogens in human and help in dropping antibiotic consumption.