Resistance to Acid and Bile Acidity
We investigated the survival rate of LAB at various
conditions, especially low pH (pH 2.0-5.0) (Table 3). In
general, each strain survived the exposure to low pH,
although the microbial count in each case decreased
markedly after 6 h. As LAB can reproduce rapidly,
survival of some cells is sufficient for their viability.
Therefore, we assumed 6 h to be sufficient to detect and
determine any apparent difference in survival ratio. The
survival ratio was tested by smearing the sample on the
plate and counting the number of cells after six hours of
incubation [20]. The CK 102 strain exhibited the highest
survival ratio of 68.2%, even at pH 2.0. In order to test
resistance against the bile, which is secreted from the
duodenum, the LAB survival ratio was investigated under
various concentrations of bile salt (0.1-1.0%). As revealed
in Table 4, CK 102 exhibited the highest survival ratio of
92.2%, even in 1% bile acid, and CK 104 also showed a
high survival ratio of 65.2%. The strains CK 102 and
CK 104 were the most bile acid resistant strains among
those tested