Antimicrobial activity of bacteriocins produced by Enterococcus isolates recovered from Egyptian homemade dairy products
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ORIGINAL ARTICLE
Antimicrobial activity of bacteriocins produced by Enterococcus isolates recovered from Egyptian homemade dairy products against some foodborne pathogens Fatma I. Sonbol 1 & Ahmed A. Abdel Aziz 1 & Tarek E. El-Banna 1 & Omnia M. Al-Fakhrany 1 Received: 3 October 2019 / Revised: 25 March 2020 / Accepted: 7 April 2020 # Springer Nature Switzerland AG 2020
Abstract The increasing mandate for fresh-like food products and the possible hazards of chemically preserved foods necessitate the search for alternatives. Bacteriocins represent a promising food biopreservative. In the present study, one hundred enterococci isolates recovered from Egyptian raw cow milk and homemade dairy products were screened for bacteriocin production. The overall detection rate was 10%. Three isolates, namely, Enterococcus faecalis (OE-7 and OE-12) and Enterococcus hirae (OE-9), showed the highest antibacterial activity with narrow spectrum against multidrug-resistant (MDR) Gram-positive foodborne bacteria: Enterococcus faecalis and Staphylococcus aureus. The antimicrobial activity was completely abolished by trypsin and proteinase K but not affected by lipase and/or amylase indicating the protein nature of the antimicrobial activity. Optimum conditions for bacteriocin production were cultivation in MRS broth at 37 °C, pH 6–6.5 for 16–24 h. The tested bacteriocins exhibited bactericidal activity on S. aureus subsp. aureus ATCC 25923; such activity was further investigated by transmission electron microscopy that revealed leakage and lysis of treated cells. Characterization of tested bacteriocins revealed high activity in a wide range of pH and temperature, storage stability, and heat resistance. PCR analysis revealed that the tested isolates produced multiple enterocins showing homology with the enterocins L50A, AS-48, and 31. Finally, this study reported potent antibacterial activity of bacteriocins derived from dairy products Enterococci against MDR foodborne and spoilage pathogens. The potency, specificity, and stability of these bacteriocins presented promising perspectives for application as biopreservatives in the food industry. The biopreservation of foods by bacteriocins produced by lactic acid bacteria recovered directly from foods remains an innovative approach. Keywords Homemade dairy products . Enterocins . Antimicrobial activity . Characterization . Food biopreservation
Introduction Recently, consumers are becoming more and more aware of the health risks posed by the consumption of chemically
* Omnia M. Al-Fakhrany [email protected] Fatma I. Sonbol [email protected] Ahmed A. Abdel Aziz [email protected] Tarek E. El-Banna [email protected] 1
Microbiology and Immunology, Faculty of Pharmacy, Tanta University, Tanta 31111, Egypt
preserved food. In contrast, there is a growing demand by the food industry to inhibit spoilage and extend the shelf-life of dairy and food products, which necessitates new preservatives (Silva et al. 2018). Bacteriocins are bacterial antimicrobial peptides with activity against
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