caused the resistance to high concentrations of bile salts to
be higher than that under acidic conditions (Sahadeva
et al. 2011). The high tolerance capability of Lactobacillus
strains under high concentrations of bile salts has been
reported by other researchers (Pan et al. 2009).
Similar to those under acidic conditions, the survival
rates for L. plantarum and L. rhamnosus strains (85–91%)
were higher than those of the other strains (L. delbrueckii,
L. casei, and L. paracasei) at a range of 69–78% at a 0.05
significance level.
Survival in simulated in vitro digestion and
adhesion assay to Caco-2 cells
One of the most desirable features of probiotics is their
capability to remain alive in the gastrointestinal tract. A
total of 17 isolated Lactobacillus were tested to evaluate
the strains further through a simulated digestion test.
Results showed that seven strains have considerable
digestion survivability. The resistant strains were three
L. plantarum and four L. rhamnosus. Five of these resistant
strains were isolated from colostrum, whereas two
were isolated from yogurt. The highest percentage of
survivability was observed for L. plantarum 17C and 13C
(both isolated from colostrum), with survivability values
of 54% and 51%, respectively (Table 2). Similar to our
results, high survival rates were reported for three commercial
probiotic strains including L. casei subsp. shirota,
L. casei subsp. immunitas, and L. acidophilus subsp.
Johnsonii in simulated digestion condition (Lo Curto
et al. 2011).
These seven digestion-resistant LAB strains were examined
for their capability to adhere to Caco-2 cells. The
results showed that L. plantarum 17C and 13C were the
most adherent strains, with adhesion values of 2.9 9 105
(3 bacteria per Caco-2 cell) and 2.6 9 105 cfu/mL
(2.5 bacteria per Caco-2 cell), respectively (Table 1).
These results are in accordance with those of other studies,
which showed that some L. plantarum strains, such as
L. plantarum L2, L. plantarum CH3 and CH41, could
adhere to Caco-2 cells better than other Lactobacilli
(Wang et al. 2009; Ramos et al. 2013).
A requirement for bacteria to be recognized as a probiotic
is their capability to remain alive while passing
through the upper digestive tract to reach the large intestine,
where their useful actions are expected. To be colonized
in the intestine, probiotic bacteria have to adhere to
the intestinal mucosa to avoid being removed from the
colon by peristalsis. Seventeen “dairy isolates” were examined
for this test. Among these isolates, only seven strains
survived exposure to the simulated digestion conditions
of the stomach. The capability to adhere to Caco-2 cells
was investigated for further analysis. We found that the