Characterization and safety evaluation of partially purified bacteriocin produced by Escherichia coli E isolated from fermented pineapple Ananas comosus (L.) Merr
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Antibacterial activity of cell-free supernatant from Escherichia coli E against selected pathogenic bacteria in food and aquaculture was the highest against Edwardsiella tarda 3, a significant aquaculture pathogen. Biochemical properties of the bacteriocins were studied and bacteriocin was found to be sensitive to proteinase K, demonstrating its proteinaceous nature. In addition, pH and temperature affected bacteriocin activity and stability. The bacteriocins were partially purified by ammonium sulfate precipitation. The antibacterial activity was only detected in 20% ammonium sulfate fraction and direct detection of its activity was performed by overlaying on the indicator strains. The inhibition zone associated with the antibacterial activity was detected in the sample overlaid by E. tarda 3 and Staphylococcus aureus DMST8840 with the relative molecular mass of about 27 kDa and 10 kDa, respectively. Bacteriocin showed no cytotoxic effect on NIH-3T3 cell line; however, two virulence genes, aer and sfa, were detected in the genome of E. coli E by PCR. The characteristics of bacteriocins produced by E. coli E exhibited the antibacterial activity against both Gram-positive and Gram-negative pathogenic bacteria and the safe use determined by cytotoxicity test which may have interesting biotechnological applications.
KeywordsBacteriocin Cytotoxicity assay Escherichia coli E Safety evaluation Virulence genes
This work was supported by a grant from Faculty of Science and Technology, Prince of Songkla University, SAT-ASEAN 5602 and SAT-ASEAN scholarship for international students 2013 to V.T. Le. Thanks are due to the Minister of Education, Malaysia, under Niche Research Grant Scheme (NRGS) vot no: R/NRGS/A0.700/00387A/006/2014/00152 for funding.
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Conflict of interest
The authors declare that they have no conflict of interest.
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