Determination of The Bacteriocin-Like Substances Produced by Enterococcus Hirae Isolated from Traditional Egyptian Food (Koskos)

Essam A. Azab¹, Sobhy E. Elsilk^{1, 2*}, Ibrahim S. Abd El-Salam ³ and  Amal M.Tahwash¹

¹Bacteriology Unit, Botany Department, Faculty of Science, Tanta University, Tanta 31527, Egypt.

²Biological Sciences Department, Faculty of Science and Art, King Abdulaziz University, Rabigh Campus, P.O. Box: 344 Rabigh 21911, Saudi Arabia.

³Natural and Microbial products, Chemistry National Research Center, Cairo.

Corresponding Author E-mail: selsilk@yahoo.de

DOI : http://dx.doi.org/10.13005/bbra/2100

ABSTRACT: The isolated organisms are screened for their antimicrobial activities against different microbial indicators. These activities expressed in inhibition zones against all tested indicator organisms. PCR products used to assess the DNA similarities and multiple sequences showed 92% identity to Enterococcus hirae (accession no.HM584102). Further identification to species level, E. hirae was based on pigment and carbohydrate formation. The SDS-PAGE analysis was indicated that bacteriocin of E. hirae is a two peptides of approximately 42 and 52 kDa. No antimicrobial activity after treatment of the cells with NaCl at pH 2.0.The leakage of K⁺ ion increased as the concentration of bacteriocin increased. The bacteriocins had a negative effect on the respiration, where the amount of consumed oxygen decreased by increasing the bacteriocins. No toxic effect against Artemia salina larva was recorded. Complete inactivation of antimicrobial activity was observed with Proteinase K and trypsin, respectively, after incubation at 37^ºC. No antimicrobial activity was recorded at pH values from 5 to 10. On the other hand, high antimicrobial activity was obtained at pH 3. Heat treatment on bacteriocin showed stability whereas non-significant results at 70^ºC or 100^ºC after 15 minutes while complete loss after incubation at 70^ºC, 100^ºC and by autoclaving.

KEYWORDS: E. hirae; bacteriocin; antimicrobial substances; characterization; Egyptian food Koskos

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