from indigenous fermented foods and human gut ... - Thapar University

Chapter II Review of Literature
survived under the acidic conditions and bile concentrations normally encountered in
fermented products and in the gastrointestinal tract, respectively. Therefore, it cannot be
generalized that all probiotic strains are acid and bile tolerant. Lankaputhra and Shah (1995)
showed that Bifidobacterium longum survives better in acidic conditions and is able to
tolerate a bile concentration as high as 4%. Acid and bile tolerance is strain dependent, and
care should be taken to select strains based on these attributes.
2.3.2.3 Adherence of probiotic bacteria
It is not clear if the adhesion to the intestinal epithelium is essential for the persistence
of a probiotic in the human intestinal tract. However, adhesion seems to be a property that
enhances long-term survival. The ability of microorganisms to adhere to epithelial cells is to
a large extent species specific, although this may be relative. Screening of organisms for their
ability to survive in the human gastrointestinal tract is not difficult. The selection of human
bacterial isolates will enhance the possibility of finding organisms that will survive. The
isolates can then be tested by administering orally between 10 9 and 10 11 viable organism in a
single dose with an appropriate buffering agent and the bacterial counts of the specific
organism are then measured in the faeces over a several week period. This technique is most
successful if the natural flora does not contain the organism being tested or only in small
numbers. The first question of transient survival can be established in 48 to 96 h. The
evaluation of the ability of the organism to permanently establish in the gastrointestinal tract,
by proliferation, can be established by continuous appearance in the faeces over several
weeks to several months. The faecal counts should exceed 10 6 /g of faeces. The application of
this screen for selecting probiotics should be encouraged in the future. There are several tests
for determining if a prospective probiotic can bind to intestinal epithelium. Radiolabelling the
microorganisms with an amino acid and then counting for adhering radioactivity in either
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