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tract, thus preventing them from adhering to IEC and also inhibiting them in this micro- environment by producing organic acids, H2O2 and bacteriocin. Competitive exclusion of two of the selected strains, i.e. L. casei LAM-1 and L. delbruckeii LKH-2, was observed in vitro against representative food-borne pathogens, suggesting a significant role in prevention of enteric infections. After screening all six strains for their functional properties, strains displaying interesting probiotic properties were then chosen for ability to produce bacteriocin. Amongst all, L. casei LAM-1 elaborated a bacteriocin with wide spectrum of action (gram positive and negative food borne pathogens) and stability under high temperature, pH and freeze thaw cycles. Most probably, bacteriocin activity results from the sum of several factors; growth-associated and stress associated mechanisms added to a possible constitutive production. According to the derived polynomial as a function of pH, temperature and time of incubation, it can be observed that production of bacteriocin by L. casei LAM-1 is regulated by different physiological factors. The bacteriocin exhibited bactericidal activity through rapid loss of ATP and K + ions by disruption of cell membranes of target pathogens; cell death was evidenced by live dead staining and scanning electron microscopy followed by transmission electron microscopy. It is recommended that colonization ability of the above mentioned probiotic isolates must be further validated through in vivo studies. Overall, this study provides a rationale for the further use of the selected L. casei LAM-1 and L. delbruckeii as probiotics for therapeutic and preventive purposes; however a prior clinical trial in humans is mandatory. The application of the bacteriocin from L. casei LAM-1for commercial purposes as biopreservative is also suggested. 143
145 Chapter V: References Aasen, I.M., Moretro, T., Katla, T., Axelsson, L. and Storro, I., 2000. Influence of complex nutrients, temperature and pH on bacteriocin production by Lactobacillus sakei CCUG 42678. Appl. Microbiol. Biotechnol. 53: 159–166. Abraham, S.N., Sharon N. and Ofek, I. 1999. Adhesion of bacteria to mucosal surfaces. In: P.L. Ogra, M.E. Lamm, J. Brenenstock and J.R. McGhene (Ed.). Mucosa Imunity. Academic Press, New York. 31-42. Abriouel, H., Ben Omar, N., Lucas, R., Martinez, C. and Galvez, A., 2006. Bacteriocin production, plasmid content and plasmid location of enterocin P structural gene in enterococci isolated from food sources. Let. Appl. Microbiol. 42: 331–337. Achemchem, F., Martinez–Bueno, M., Abrini, J., Valdivia, E. and Maqueda, M., 2005. Enterococcus faecium F58, a bacteriocinogenic strain naturally occurring in Jben, a soft, farmhouse goat’s cheese made in Morocco. J. Appl. Microbiol. 99: 141–150. Achen, M. and Yousef, A.E., 2001. Efficacy of ozone against Escherichia coli O157:H7 on apples. J. Food. Sci. 66: 1380-1384. Alakomi, H.L., E. Skytta, M. Saarela, T. Mattila-Sandholm, K. Latva-Kala and Helander, I.M., 2000. Lactic acid permeabilizes gram-negative bacteria by disrupting the outer membrane. Appl. Environ. Microbiol. 66: 2001-2005. Alander, M., R. Satokari, R. Korpela, M. Saxelin, T. Vilpponen-Salmela, Mattila- Sandholm, T. and von Wright, A., 1999. Persistence of colonization of human colonic mucosa by a probiotic strain, Lactobacillus rhamnosus GG, after oral consumption. Appl. Environ. Microbiol. 65: 351-354. Albano, H., todorov, S. D., Van Reenen, C. A., Teixera, P. and Dicks, L. M. T. 2011. Characterization of two bacteriocins produced by Peliococcus adidilactici isolated from
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Characterization of Lactobacilli is
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their encouragement, insightful com
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5. Mukesh Kumar and Abhijit Ganguli
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2.3.2.9 Cholesterol lowering 2.3.2.
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3.12.4 Measurement of intracellular
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List of Abbreviations ABTS 2,2-azin
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LIST OF TABLES Tables Page No. Tabl
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Chapter 1 INTRODUCTION
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2 Chapter I: Introduction Recent re
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4 Chapter I: Introduction Gram-posi
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6 Chapter I: Introduction food-born
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Chapter I1 REVIEW OF LITERATURE
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4.6 Molecular characterization of t
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91 Chapter IV: Results Table 4.12 A
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