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

Chapter II Review of Literature
2000). In humans, excess bile deconjugation may lead to adverse effects such as steatorrhea
and formation of secondary bile salts, which are toxic and/or mutagenic (Marteau et al.,
1995).
Probiotics have also been shown to modulate the immune system at different levels.
They may have anti- and/or pro-inflammatory properties. Some strains have shown to
influence the adaptive immunity, whereas others affect the innate immunity (Fuller and
Perdigon, 2000).
2.3.4 New probiotic strains and sources of isolation
There is still no consensus about the need for viability of probiotics to exert health
effects (Gopal et al., 2001). Some studies maintain that the viability of probiotic strains is
necessary for stimulation of the gut associated immune system (Lammers et al., 2002) or for
anti-genotoxic effects (Galdeano and Perdigon, 2004; Ma et al., 2004). Others have shown
that heat-killed probiotics (Pool-Zobel et al., 1996), or specific components derived from
probiotic strains such as DNA (Nagy et al., 2005) or bacterial cell wall (Lammers et al.,
2002; Jijon et al., 2004) are responsible for some immunomodulatory effects. If this is the
case, and live microorganisms are not necessary to obtain the desired effects, a revision of the
definition of probiotics or the development of a new concept defining these probiotic-derived
components will be needed.
A general agreement among those in favor of the classical definition of probiotics,
refers to the need of live microorganisms exerting health-promoting effects, and thus, the
need of survival in host conditions to reach the site of action. The general criteria for
selection of strains to be used as probiotics include: safety and origin of the bacteria, their
tolerance to the hostile conditions of the stomach and small intestine, and their ability to
adhere gut epithelial tissue (Davidkova et al., 1992; Tannock, 2002). The first step in the
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