UBC Theses and Dissertations
Characterization of the major antimicrobial components of the Chilean tinamou (Nothoprocta perdicaria) egg white Varon, Orly
Chilean tinamou (Nothoprocta perdicaria) egg white was characterized and compared to chicken (Gallus gallus) and emu (Dromaius novaehollandiae) egg whites for composition and antimicrobial components. Tinamou and chicken appeared more similar in terms of protein, sialic acid, ash, and iron content than tinamou and emu, even though phylogenetic analysis places tinamous within the ratites. Egg white proteins were separated by anion–exchange Fast Protein Liquid Chromatography, followed by SDS–PAGE. Tinamou ovotransferrin, ovomucoid, and lysozyme C were identified by peptide mass fingerprinting of SDS-PAGE bands. Similar sized ovotransferrins were present in all egg whites species, however higher quantities were observed for ratites. It is possible that ovotransferrin has an essential antimicrobial function and therefore its presence is conserved among distinct species. The antimicrobial activity of tinamou and chicken ovotransferrins against two food related pathogens, Escherichia coli O157:H7 and Staphylococcus aureus COL was bicarbonate, concentration, and avian species dependent, as evaluated by turbidly and viability assays. Native ovotransferrins were the most effective against E. coli O157:H7, followed by apo and holo forms. Native ovotransferrins exhibited a significant bactericidal activity at a concentration of 10 mg/ml with bicarbonate. In the presence of bicarbonate, chicken apo and holo ovotransferrins were more bacteriostatic than tinamou ovotransferrins. Additionally, there was no significant difference in the antimicrobial activity of apo and holo ovotransferrins applied at 5 and 10 mg/ml. Holo ovotransferrins exhibited moderate antimicrobial activity, only in the presence of bicarbonate; therefore it is possible that bicarbonate contributes to the antimicrobial activity of ovotransferrin by a mechanism other than a bridging ligand between ovotransferrin and iron. Native chicken and tinamou ovotransferrins at 10 mg/ml were bactericidal against S. aureus COL, whereas tinamou ovotransferrin was more bacteriostatic. In conclusion, tinamou ovotransferrin combined with bicarbonate was found to be bactericidal against two foodborne pathogens. In the absence of bicarbonate, tinamou ovotransferrins exhibited minor bacteriostatic activity, while chicken ovotransferrin was not effective. It is possible that tinamou ovotransferrin possesses different amino acid sequences from the chicken protein that form unique antimicrobial motifs; therefore it should be further investigated as a natural antimicrobial agent for use in food matrices or food preparation surfaces.
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