A suspension of each isolate in PBSwas made. One ml of probiotic
suspension adjusted to an OD600 of 0.220 was inoculated into
nine ml of standard MRS broth (positive control), modified MRS
broth supplemented with hydrochloric acid to reach pH 2.0 and 4.0,
and modified MRS broth supplemented with 0.15% and 0.3% (w/v)
bovine bile (Oxoid). Bacterial growth was measured spectrophotometrically
at OD600 immediately after inoculation and following
24 h and 48 h of aerobic incubation at 37 C. The difference in OD600
measurements between the first (time 0) and the last (48 h)
measurement in standard MRS broth was defined as 100% growth.
The increase in OD600 observed during culture in modified MRS
broth was expressed as a percentage compared to growth in the
standard MRS broth. Each test was performed in duplicate