| The overall goal of this study was to develop practical, natural, and efficient antimicrobials from egg. To accomplish the goal, novel protocols for large-scale production of egg yolk immunoglobulin and ovotransferrin were developed. Also antibacterial activity of ovotransferrin against Escherichia coli O157:H7 and Listeria monocytogenes was investigated and the antimicrobial activity of ovotransferrin was improved by combinations with other antimicrobials. The developed protocol for large-scale production of egg yolk immunoglobulin (IgY) consisted of several steps such as using 0.01% charcoal to remove lipoproteins from IgY extract, ultrafiltration to concentrate IgY solution, and 40% ammonium sulfate to precipitate IgY following dialysis. Morevoer, apo-ovotransferrin was isolated from 2 time-diluted egg white by following steps: as iron saturation of egg white, extraction of iron-bound (holo) ovotransferrin using 43% ethanol, precipitation of holo-bound ovotransferrin by 59% ethanol, dissolving the precipitate with distilled water, and removal iron from holo-ovotransferrin using AG RTM1-X 2 ion exchange resin. After separating apo-ovotransferrin, the effects of citric acid, Zn- and Fe- binding, and sodium bicarbonate (NaHCO3) on the antibacterial activity of ovotransferrin against E. coli O157:H7 and L. monocytogenes in model systems using BHI broth were investigated. Synergistic effects of EDTA and lysozyme on the antimicrobial activities of ovotransferrin were investigated toward E. coli O157 and L. monocytogenes on model systems using BHI broth and pork chops and hams.; According to this study, IgY obtained by developed protocol was approximately 70--80% recovery and approximately 80% purity. The new procedure seems to be economical and practical for a large-scale purification of IgY from egg yolk since ammonium sulfate precipitation could accommodate of large volume of egg yolk. Also, the recovery rate and purity of ovotransferrin produced by the newly developed protocol was around 94% and 80% respectively. As the procedure is consisted of only a few steps, it is suitable to a large-scale production of ovotransferrin. Also becasuse ethanol and AG RTM1-X 2 ion exchange resins can be regenerated, it seems to be economical and efficient. In study related to antibacterial activity of ovotransferrin, 100 mM-NaHCO3 significantly increased the antibacterial activity of ovotransferrin against both E. coli O157:H7 and L. monocytogenes. 0.5% citric acid enhanced the antibacterial activities of ovotransferrin against E. coli O157:H7, Zn-bound ovotransferrin appeared to inhibit the growth of L. monocytogenes. So, this study suggests that the iron binding capacity of ovotransferrin was not the major mechanism of antimicrobial actions of ovotransferrin because acidic pH or Zn2+ promotes antibacterial activity of ovotransferrin toward E. coli O157:H7 or L. monocytogenes respectively. Also, 2 mg/ml EDTA improved antibacterial activity of ovotransferrin containing 100 mM-NaHCO3 against E. coli O157:H7. Also when lysozyme was combined with OS, the antibacterial activity of OS against L. monocytogenes increased slightly in vitro test. However, synergistic effect of lysozyme on antimicrobial activity of OS against L. monocytogenes did not show significantly in this study. Contrary to the model system results using BHI broth, ovotransferrin plus EDTA or/and lysozyme did not show any antimicrobial activities toward E. coli O157:H7 and L. monocytogenes in pork chops and hams.; Developing preservatives such as IgY and ovotransferrin are significant not only for the food industry but also for consumers because they are derived from natural sources and generally regarded as safe. Use of these products will significantly increase the value of eggs, which is important for egg industry. Furthermore, this study claims that ovotransferrins combined with NaHCO3, EDTA, or lysozyme have high potential as natural antimicrobial agents to control E. c... |
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