Abstract
Bacteriocins from lactic acid bacteria (LAB) are natural antimicrobial peptides or proteins with interesting potential applications in food preservation and health care. The present study was aimed to isolate bacteriocinogenic LAB from dairy products, fermented food and environmental waste samples. One thirty five colonies of LAB were isolated and screened for bacteriocin production by agar overlay method. Among them, Lactobacillus acidophilus NCIM5426 isolated from home made paneer showed maximum zone of inhibition i.e 22-24mm in diameter against food borne (Listeria monocytogenes, Staphylococcus aureus) and human pathogens (Escherichia coli, Salmonella typhi). The antibacterial compound from the culture supernatant was found to be proteinaceous in nature and therefore, identified as bacteriocin. The bacteriocin of L. acidophilus NCIM5426 was found to be heat-stable (1210C for 15 min) and active over a wide pH range of 4.0-10.0. It showed stability (60%) for 30 days at room temperature (30-320C). Addition of surfactants (EDTA, SDS, Hexadecyl trimethylamonium bromide) up to 1% to crude bacteriocin showed increase in antibacterial activity where as metal ions (Calcium Chloride, Zinc Sulphate and Mercuric Chloride) in low concentration (0.5-1mgL-1 ) decreased the activity. The bacteriocin was purified to its homogeneity by ammonium sulfate precipitation followed by gel filtration chromatography and HPLC. Molecular weight of bacteriocin was found to be 5.6 and 5.8 KDa by SDS page and LC/MS respectively. Production and activity of bacteriocin was significant (50%) even at higher salt (NaCl) concentration i.e 3%. Our present study demonstrates the possibility of using L. acidophilus NCIM5426 or its bacteriocin as a biopreservative in dairy industry. Keywords: Antibacterial activity, Bacteriocin, Lactic acid bacteria, Lactobacillus acidophilus
Highlights
Lactic acid bacteria (LAB) are traditionally used as dependent secreted bacteriocins; class III, large, heatstarter cultures for the fermentation of foods and labile protein bacteriocins
The L. acidophilus group of LAB is have the property of inhibiting other bacteria, either of the widely used in milk products such as same species or across genera
Bacteriocins of antimicrobial peptide from L. acidophilus that was LAB are of particular interest because of their existing undoubtedly identified as a bacteriocin (Oh et al, 2000)
Summary
Lactic acid bacteria (LAB) are traditionally used as dependent secreted bacteriocins; class III, large, heatstarter cultures for the fermentation of foods and labile protein bacteriocins. The main objective of the present study is to evaluate the nature of the antibacterial compound (bacteriocin) from L. acidophilus NCIM5426 isolated from dairy sample. The crude bacteriocin sample from L. acidophilus NCIM5426 was characterized for stability to proteolytic enzyme (trypsin), heat, pH, surfactants, storage and metal ion.
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