BILE AND ACID TOLERANCE ABILITY OF PROBIOTIC LACTOBACILLUS STRAINS

Abstract

Lactobacillus makes up an extremely important group of probiotic bacteria and is used in many probiotic dairy products. Probiotics are live microbial food supplements which beneficially affect the host by improving the intestinal microbial balance. Probiotic bacteria used as food adjuncts are commonly delivered in a food system and their journey starts from the mouth to lower intestinal tract. Therefore probiotic bacteria must overcome physical and chemical barriers such as bile and acid in the gastrointestinal tract. Hence, tolerances to bile and acid are the two most important properties for selection of potential probiotic strains. The aim of this research was to find out the ability of bile and acid tolerance of the three isolates namely Lactobacillus plantarum CM 25, Lactobacillus. casei subsp.  rhamnosus CM 33 and Lactobacillus. casei subsp. casei CM 34. Bile tolerance of the isolates was tested against three concentrations 0.1%, 0.2% and 0.3% of sodium glycocholate and sodium taurocholate both. With increase in the concentration of bile salts the growth of all the isolates was decreased. Among all the three isolates tested Lactobacillus plantarum CM 25 and Lactobacillus casei subsp. casei CM 34 showed highest survival at 0.3% concentration of sodium glycocholate and sodium taurocholate respectively. Among the two bile salts used, more tolerance of the isolates was found against sodium taurocholate. Acid tolerance of the isolates was tested at various acidic pH values ranging from pH 2.0 to 6.0. Survival percentage of all the three isolates decreased along with the decrease in pH. Lactobacillus plantarum CM 25 showed the highest survival at pH 2.0. These findings suggest that all the three Lactobacillus isolates are capable to grow in the presence of bile salts and acid.