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    Enterocin HZ produced by a wild Enterococcus faecium strain isolated from a traditional, starter-free pickled cheese
    (CAMBRIDGE UNIV PRESS, 2014) Yildirim, Zeliha; Bilgin, Harun; Isleroglu, Hilal; Tokatli, Kader; Sahingil, Didem; Yildirim, Metin
    Bacteriogenic Enterococcus faecium HZ was identified by using biochemical (Strep-API 20, API-50 CHL, fatty acid profile) and 16S rRNA analysis (99 center dot 99%). Ent. faecium HZ was sensitive to clinically important antibiotics such as vancomycin, and did not have gelatinase and haemolysis activities. Enterocin HZ, a bacteriocin from Ent. faecium HZ, was sensitive to papain and tyripsin, but resistant to pepsin, lipase, catalase, alpha-amylase, organic solvents, detergents, ss-mercaptoethanol, and heat treatment (90 degrees C/30min). It was biologically active at pH 2 center dot 0-9 center dot 0 and synthesised at the highest level in MRS or M17 broth at 32 or 37 degrees C with an inoculum amount of 0 center dot 1-0 center dot 5% and an initial pH of 6 center dot 0-7 center dot 0. Enterocin HZ production reached maximum level at middle and late logarithmic phase and its molecular weight was similar to 4 center dot 5kDa. It was active against some Gram-positive foodborne bacteria. Ent. faecium HZ or its bacteriocin enterocin HZ is a good candidate to be studied as a food biopreservative since enterocin HZ showed strong bactericidal activity against Listeria monocytogenes in UHT milk and also Ent. faecium HZ grew very well in milk and produced enterocin HZ at maximum level.
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    Inhibitory effect of enterocin KP in combination with sublethal factors on Escherichia coli O157:H7 or Salmonella Typhimurium in BHI broth and UHT milk
    (TUBITAK SCIENTIFIC & TECHNICAL RESEARCH COUNCIL TURKEY, 2014) Yildirim, Zeliha; Ilk, Yaselin; Yildirim, Metin; Tokatli, Kader; Oncul, Nilgun
    The effects of physical and chemical sublethal treatments on the antibacterial activity of enterocin KP produced by Enterococcus faecalis KP against Escherichia coli O157:H7 and Salmonella Typhimurium were investigated. Enterocin KP was not active against intact cells of E. coli O157: H7 or S. Typhimurium. However, the use of enterocin KP together with ethylenediaminetetraacetic acid (50 mM), sodium tripolyphosphate (50 mM), sublethal heating (60 degrees C for 10 min), cold shock (-20 degrees C for 2 h), or acid stress (mixture of 40% lactic acid, 16% propionic acid, 16% acetic acid) in BHI medium decreased the cell number of E. coli O157: H7 by 7.27, 6.28, 3.39, 3.06, 4.20 log and S. Typhimurium by 7.21, 6.20, 3.64, 3.38, 3.98 log cfu/mL, respectively. The combination of enterocin KP with ethylenediaminetetraacetic acid decreased the cell number of E. coli O157: H7 in UHT milk to undetectable level, enterocin KP plus sodium tripolyphosphate or enterocin KP plus sublethal heating caused a reduction by 6.07 and 5.68 log cycles. The results of this study showed that enterocin KP could be applied as a biopreservative to inhibit E. coli O157: H7 and S. Typhimurium in combination with physical and food grade chemical hurdles.
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    The inhibitory effect of lactoccocin BZ against Escherichia coli on fresh beef
    (M H Schaper Gmbh Co Kg, 2024) Oncul, Nilgun; Tokatli, Kader; Yildirim, Zeliha
    During the processing of fresh meat, there is a risk of contamination with foodborne pathogenic E. coli. The use of bacteriocins is considered to ensure the safety of fresh meat. In this context, the impact of lactococcin BZ on the E. coli population in fresh beef has been investigated. The antibacterial activity of lactococcin BZ was observed in meat samples inoculated with E. coli both during and after attachment condition (10(3) and 10(6) CFU/mL), and over a 12 days storage period in refrigeration (4 degrees C). Different amounts of lactococcin BZ (ranging from 400 to 3200 AU/mL) were applied to fresh meat for varying treatment durations (0-30 minutes). Following the application of lactococcin BZ at levels of 800, 1600, and 3200 AU/mL during attachment, E. coli counts were immediately reduced by 3.62 log units. At high inoculum dose, lactococcin BZ (3200 AU/mL) decreased the pathogen by approximately 6 log units in 5 minutes during attachment. E. coli exhibited sensitivity to lactococcin BZ (400, 1600, and 3200 AU/mL) both in low and high inoculum doses after attachment to fresh beef. Furthermore, the inhibitory effect of lactococcin BZ increased with its concentration over the 12 days of refrigerated. In conclusion, lactococcin BZ demonstrated inhibitory effect against E. coli in fresh beef, suggesting its potential use as a biopreservative in the meat industry.