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Chapter V Discussion
Lactobacillus is a normal inhabitant of the gut ecosystem (Tannock, 1999), and therefore it is
not surprising, that they possess the capability to sustain conditions of gut. The strain L.
casei, which was originally isolated from the fermented milk, is a known probiotic strain that
is commercialized in country including india. This could also be an interesting alternative for
developing a probiotic product without milk constituents using the L. casei strains
characterized in this study. However, the two selected L. delbruckeii strains isolated from
Kharoli, were present in low numbers in this product and were not representatively important
as predominant species in the microbiota of this traditional fermented food.
L. casei LAM-1 survived under low pH conditions for five hours and well tolerated
bile acids under in vitro conditions even at concentrations higher than those previously used
by other authors (Jacobsen et al., 1999; Fernández et al., 2003). Acid tolerance of bacteria is
an important factor to assure their resistance of gastric stresses and also for their use as
dietary adjuncts in acid foods such as yoghurt.
Resistance to bile salts is considered as an important property for strains to be used as
probiotics, however, there is still no consensus about the precise concentration to which the
selected strain should be tolerant. The physiological concentration of bile acids in the small
intestine varies from 5 to 20 mM/l (Hofmann, 1991). Therefore, a concentration of 0.5% ox-
gall, equivalent to 12.25 mmol/l bile acids was used in this study, as was also previously done
by Kociubinsky et al. (1999). This concentration is higher than the ones (0.3% and 0.15%)
previously used by other investigators for judging bacterial probiotic properties (Chou and
Weimer, 1999; Zarate et al., 2000; Fernandez et al., 2003).
Another test for resistance to intestinal conditions used in this study was resistance to
0.4% phenol. Phenols may be formed in the intestine as a result of the bacterial deamination
of some aromatic amino acids derived from dietary and endogenous proteins. These