The in vitro low pH and high concentrations of bile
salts tolerance experiments show the same cell viability
results. The assessment of the harsh condition tolerance
of probiotic bacteria can be performed by using an
in vitro method with the same pH (pH 2.5) or concentration
of oxgall [0.3% (w/v)] in the gastrointestinal tract
(Ben Salah et al. 2012).
The survival rates for 17 isolated Lactobacillus strains
after 3 h of incubation at pH 2.5 and the substance at
0.3% (w/v) high concentrations of bile salts are shown in
Table 2. All isolates displayed high growth at low pH and
high concentrations of bile salts.
The isolates showed high survival rates of more than
57% of that of other strains under low pH conditions.
The survival rates of the L. plantarum and L. rhamnosus
strains (76–82%) were also significantly higher than those
of the other strains (L. delbrueckii, L. casei, and L. paracasei),
which ranged from 57% to 65%, at a 0.05 signifi-
cance level. These results are in accordance with those of
other studies, which showed that some Lactobacillus
strains, such as L. plantarum, tolerate low pH conditions
better than other strains (Abriouel et al. 2012).
The isolates displayed higher tolerance of high concentrations
of bile salts conditions (≥69%). The high concentrations
of bile salts tolerance capability was strain specific,
similar to the case under acidic conditions. The effects of
high concentrations of bile salts on bacterial cells can be
distinguished from the acidic effects, but some combined
results can be observed. Stress adaptation mechanisms