| Ovotransferrin, a kind of glycoprotein that possesses high content in chicken egg white, could bind two Fe3+ irons and displays thermolability. It can reversibly bind two Fe3+ irons, as a result it owes strong antimicrobial activity against various microorganism. Also it could be applied as novel functional additive in food industry widely to prolong the shelf life and improve the health of human beings. Nowadays there are several problems in the study on the separation of ovotransferrin from egg white, such as protein is degenerated during separation, the purity of protein product is particularly low, also the studies are all laboratory studies and could not be scaled up. Hence it is extremely significative for the development of egg products deep processing to explore a new way to separate ovotransferrin. In recent years, magnetic nanoparticles gets an increasing number of attention in the field of protein separation since the nanoparticles could be located and separated rapidly. Therefore the application of functional magnetic nanoparticles in the separation of ovotransferrin from egg white is studied in this paper. Besides, to study on ovotransferrin heat stability thoroughly could provide theoretical basis for the egg products process design and for the application of ovotransferrin as a natural antibacterial agent in food industry.Firstly Fe3O4 core is prepared and decorated by TEOS and APTMS to get Fe3O4@Si O2-NH2 nanoparticles. Then functional groups, size, zeta potential and magnetic properties of the nanoparticles are studied. Results show that silica shell and amino groups are successfully decorated onto the surface of nanoparticles, the mean size is about 210 nm and the isoelectric point(p I) is approximately 9.25, in addition the nanoparticles display excellent dispersity, high stability and desirable magnetic properties. Hence the functional Fe3O4@Si O2-NH2 nanoparticles possess the potential to separate ovotransferrin.Afterwards the functional Fe3O4@Si O2-NH2 nanoparticles are applied in the adsorption of ovotransferrin from egg white. The best temperature and p H for adsorption are 40 oC and 7.4, respectively. Also the adsorption kinetics are described by pseudo kinetic model. The eluted ovotransferrin has high purity of 81.02% detected by HPLC and the recovery reaches 84.62%, besides the protein owns well functional performance since it shows a high capacity to combine with iron ion. The Fe3O4@Si O2-NH2 nanoparticles shows desirable repeatability in repeated adsorption-desorption experiments for thirty times, as the maximum adsorption still remains more than 70 mg/g and the recovery of Fe3O4@Si O2-NH2 nanoparticles reaches more than 70%. Therefore Fe3O4@Si O2-NH2 nanoparticles are ideal candidates of magnetically targeted protein carriers for separating ovotransferrin from chicken egg white due to the huge advantages of high adsorption, good separating effect, and satisfactory repeatability. Also the study proposes a possibility to scale up the separation of ovotransferrin.Study on ovotransferrin heat stability shows that ovotransferrin is highly sensitive to heat, as even long-time process in 65 oC would lead to the degeneration. After heat treatment, the relative content of the secondary structure in ovotransferrin changes greatly. The unfolding of tryptophan residues leads to the increase of surface hydrophobicity. Besides the destruction of cystine disulfide bond does exert a great influence on the antibacterial effect of OVT. The antibacterial effectdecreases but not fully loses after dealt with 65 oC and 75 oC, and after disposed at 85 oC and 95 oC the antibacterial effect shows no apparent changes as the protein has been mainly degenerated. Hence in the process of ovotransferrin, high level of heat treatment should be avoided to maintain the antibacterial effect and other functional properties of ovotransferrin. |
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