Effect of Pulsed Electric Fields on the Antibacterial Activity of Ovotransferrin and Mechanism of Action

Abstract

Ovotransferrin (OVT) is an iron-binding glycoprotein, found in egg white and serum. It appears to be a multi-functional protein with a major role in avian natural immunity and antimicrobial activity. In this study, the effects of high-intensity pulsed electric fields (HIPEF) on antibacterial activity of OVT particularly for Escherichia coli and the changes in its iron-binding capacity were investigated. Fluorescence spectra technology was used to analyze possible structural changes of OVT, explaining and exploring the effects of the HIPEF technology on the mechanisms that determine the protein activity. The results showed that when the electrical field intensity was 40 kV.cm-1, the antibacterial activity of OVT solution was the highest 87.9% as compared to the control (6.052×107CFU.mL-1) and iron-binding capacity reached the maximum 0.733, which was 2.4 times higher as compared to the control. When the pulse number reached at 80, the antibacterial activity of OVT solution increased up to 74.5% as compared to the control (6.052×107CFU.ml-1) and iron-binding capacity was 1.9 times higher than that of control. With the change of pH values from 7.0 to 8.0, the iron-binding capacity was slightly decreased, the difference was not significant among the groups (P>0.05). Fluorescence spectra analysis showed that the microenvironment of OVT changed with the increase of the pulsed electric field intensity and number and changes in the fluorescence intensity were measured constantly with fluroescensce quench phenomena occurring. The fluorescence intensity was reduced to minimum at 40 kV.cm-1or 80 pulse number. The results showed that the changes of the iron-binding capacity after HIPEF treatment were strongly linked with the changes of the antibacterial activity. An increase of the electrical field intensity and change in treatment time induced higher inhibition of Escherichia coli with OVT.