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

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Chapter I: Introduction
food-borne illness in outbreaks during years 1975-2006 (Niskanen et al., 2007). Clearly, food
and water safety need to be improved.
Microbes have an extraordinary array of defense systems. These include classical
antibiotics, metabolic by-products such as lactic acid, numerous types of protein exotoxins,
and antimicrobial peptides such as bacteriocins. The most promising antimicrobial peptides
are those produced by LAB. Most LAB bacteriocins are non-toxic to eukaryotic cells and are
generally recognized as safe substances, active in the nanomolar range (Cotter et al., 2005;
Peschel and Sahl, 2006). LAB antimicrobial peptides typically exhibit antibacterial activity
against food-borne pathogens, as well as spoilage bacteria. Therefore, they have attracted the
greatest attention as tools for food biopreservation (Collins et al. 1998; O’Sullivan et al.,
2002; Reid et al., 2003). They either show bacteriostatic or bactericidal activity against
targeted pathogens. Probiotics are now widely available commercially and marketed through
food products such as yoghurt, fermented milks, fermented juices and freeze dried
supplements. As commercially available probiotic strains are being produced and marketed
for human consumption on a large scale, it is important to identify them at species and strain
level.
In past 10 years, there has been an increase in the consumption of probiotics and
functional foods in Western diets (O’sullivan, 1996). Probiotic bacteria are able to suppress
potentially pathogenic microorganism in the gastrointestinal tract and enhance the population
of beneficial microorganisms (Yaeshima et al., 1997). The health benefits derived by the
consumption of foods containing probiotic bacteria are well documented and more than 90
probiotic products are available worldwide. To provide health benefits, the suggested
concentration for probiotic bacteria is 10 6 CFU/g of a product (Shah, 2000). However, studies
have shown low viability of probiotics in market preparations (Shah et al., 1995). A number