Evaluation of probiotic potential of lactic acid bacteria isolated from traditional fermented milks byin vitrostudy

Abstract

Probiotic potential of five lactic acid bacteria ('Lactobacillus rhamnosus' NK2, 'Lactobacillus casei' NK9, 'Lactobacillus rhamnosus' NK10, 'Lactobacillus pentosus' M20 and 'Lactobacillus plantarum' M22 ) was carried out by performing a battery of 'in vitro' tests i.e. low pH tolerance, tolerance to high bile concentration, cell surface hydrophobicity, bile salt hydrolase and antimicrobial activity. These isolates were able to tolerate upto pH 2.0 for 3h and 0.5% oxgall upto 4hrs. Hydrophobicity against toluene and xylene was found in the range of 42.48% to 77.80% and 37.97% to 75.39%, respectively. Bile salt (0.5% sodium taurocholate) hydrolase activity was found only in 'L. plantarum' M22. The antimicrobial activity was measured using cell free supernatant (CFS) and neutralized CFS (pH 7) against four indicator strains ('Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus and Salmonella typhi'). All the isolates were able to producezone of inhibition with CFS depending on the indicator strains but with neutralized CFS, 'Lactobacillus rhamnosus' NK2 was failed to inhibitS. typhi,L. casei NK9 was failed to inhibit 'Listeria monocytogenes, S. aureus and S. typhi' while 'L. rhamnosus' NK10, 'L. pentosus' M20 and 'L. plantarum' M22 couldn't produce inhibition zone against 'Listeriamonocytogenes' and 'S. aureus. L. plantarum' M22 could be a potential probiotic isolate compared to others.