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Mainak Bhattacharjee
1* Department of Biotechnology, Heritage Institute of Technology, Chowbaga Road, Ananadapur, P.O-East Kolkata Township, Kolkata-700107, West Bengal.
Former Lecturer, Department of Microbiology, Duragapur College of Commerce and Science (DCCS), G.T.Road, Rajbandh, Durgapur-713212, West Bardhhaman Dist., West Bengal
Monojit Banerjee
2 Department of Biochemistry, Triveni Devi Bhalotia (TDB) College, Raniganj, Dist-West Bardhhaman, West Bengal-713347
Jayashree Deb
3 Department of Biotechnology, Duragapur College of Commerce and Science (DCCS), G.T.Road, Rajbandh, Durgapur-713212, West Bardhhaman Dist., West Bengal
Abstract
The present study involves isolation followed by morphological and physiological characterization of a bacteriocin-producing Lactic Acid Bacillus (LAB) species from a commercially available packaged lassi (curd or yoghurt based probiotic drink; widely consumed in Indian subcontinent) sample followed by the partial purification and characterization of the bacteriocin protein by ammonium sulphate precipitation and dialysis. Bacteriocins are proteinaceous compounds produced by a wide group of bacteria that have anti-bacterial activity against closely related species. The anti-bacterial activity of the crude bacteriocin produced by the lassi LAB isolate was tested against 3 indicator bacteria-Bacillus subtilis, Staphylococcus aureus and E.coli and it was observed that the bacteriocin was most effective at 370C temperature and at pH 3.0-4.0 as measured by the diameter of the inhibition zone against all the 3 indicator organisms. The protein retained considerable inhibitory effect up to 600C temperature indicating its partial thermostable nature. Maximum inhibitory effect was found against Bacillus subtilis while E.coli was the least sensitive. The proteinaceous nature of the crude bacteriocin was confirmed by trypsin treatment and as the protein was found to be degraded by increasing concentrations of trypsin treatment, it makes it safe for human consumption. UV-radiation was found to have no effect on the anti-bacterial action of the crude bacteriocin protein. Since the bacteriocin was considerably effective against Staphylococcus aureus, a common food-borne pathogen, it could be potentially used as a natural antibiotic against this bacterium and at the same time, it also has an industrial application as a bio-preservative for fermented milk products having acidic pH if more specialized methods for its purification and toxicity analysis are adopted.
KEYWORDS: Probiotic, Lactic Acid Bacteria (LAB), Bacteriocin, anti-bacterial activity, bio- preservative.