High bile- and low pH-resistant lactic acid bacteria isolated from traditional fermented dairy products in Inner Mongolia, China

Abstract

 To create probiotic fermented dairy products by lactic acid bacteria which have a potential to colonize the intestinal tract, 122 strains, which were isolated from traditional fermented dairy products in Inner Mongolia, China, were supplied to bile tolerance and simulated digestive juice tolerance trials as indicator tests of probiotics. Growth rate (OD_{620 nm}) after 6 hours incubation in MRS broth supplemented with 0.3% oxgall, tolerance to artificial gastric juice adjusted pH2.0 or pH3.0 and tolerance to artificial intestinal juice were measured by viable cell count. Biochemical, physiological and genetic properties, activity of enzyme (APIZYM) and acid production in reconstituted skim milk of selected strain were investigated. Strain 301102 that growth rate in MRS broth containing 0.3% oxgall was 60%, survival rate after 3 hours in artificial gastric juice adjusted pH2.0 was 71%, and showed tolerance in artificial intestinal juice was finally selected. This strain was identified as Lactobacillus plantarum from biochemical and physiological properties. As a characteristic of this strain, the tolerance to the bile was extremely high by growing in MRS broth containing 20% oxgall. Moreover, protease activities were little or none except for leucine aminopeptidase. The activity of acid production was improved by adding 0.1% soy peptides or yeast extract to reconstituted skim milk, and the titratable acidity after incubation for 24 hours rose up to 1.0%. Lactobacillus plantarum 301102 could use as starter of probiotic fermented dairy products and conduce to probiotic effect by well growth in intestinal tract after ingestion.