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Molecular Characterization of Bacteriocin Producing LAB by Quorum Sensing Mechanism

Anusha, P. (2009) Molecular Characterization of Bacteriocin Producing LAB by Quorum Sensing Mechanism. [Student Project Report]

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Abstract

This Dissertation / Report is the outcome of investigation carried out by the creator(s) / author(s) at the department/division of Central Food Technological Research Institute (CFTRI), Mysore mentioned below in this page.

Item Type: Student Project Report
Additional Information: The isolation of bacteriocinogenic cultures was carried out from food sources like vegetables, dairy products and pickle by pour plating. Specific screening assays were evaluated for identification of QS dependant bacteriocinogenic LAB isolates by different methods viz. deferred antagonism method, spot on lawn, and well diffusion assay using Listeria monocytogenes Scott A as indicator organism. A spot on lawn assay was optimized for detecting QS dependant bacteriocin producers based on studies on growth curve and bacteriocin biosynthesis in standard bacteriocinogenic Enterococci- Enterococcus faecium DPC 1146 and E. faecium MTCC 5153. Three QS dependant cultures showing potent antilisterial activity were studied further. The bacteriocin activity of two fold diluted culture filtrate was measured in terms of arbitrary units by following critical dilution method. These cultures showed antibacterial activity against several pathogens such as Salmonella typhi, Bacillus cereus and other listerial strains with a bacteriocin activity of upto 1600 AU/ml using L. innocua as indicator. Crude bacteriocin preparation of the CF exhibited heat tolerance upto 1200 C and pH stability from 6-10. The bacteriocin preparation was sensitive to several proteolytic enzymes such as papain trypsin, proteinase K, except pepsin treated at a concentration of 1mg/ml, at 370C for 1 hour. Bacteriocin induction assays using CF as source of IF at different Temperature, pH and proteolytic enzymes treatment were carried out for standard and native food isolates. The LAB isolates identified in the present study produced bacteriocins against Listeria, one of the important food borne pathogens and other pathogenic bacteria. The QS mode of bacteriocin production by these cultures can be exploited as a food grade heterologous gene expression system. The abiotic and biotic factors influencing the bacterion production and induction is useful for selecting foods to exploit these cultures as a source of in situ bacteriocin production. As the bacteriocins show pH stability at 2-8, they can be applied in foods with both acidic and alkaline pH, to increase their shelf life. The temperature stability of bacteriocins is also helpful in applying them in processed foods.
Uncontrolled Keywords: Lactic acid bacteria Bacteriocins Quorum Sensing
Subjects: 500 Natural Sciences and Mathematics > 07 Life Sciences > 04 Microbiology
Divisions: Food Microbiology
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 03 Jun 2009 09:54
Last Modified: 28 Dec 2011 10:08
URI: http://ir.cftri.com/id/eprint/8982

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