Purification of IgY from egg yolk

Jensenius et al. (1981) reported two methods which circumvent many of the earlier problems for the isolation of IgY. The yolk, of which 50% is non-aqueous, is separated from the egg white and its membrane is cut open. The yolk (20 ml) is diluted with 80 ml TBS (10 mM Tris-HCl buffer, pH 7.4, and 140 mM NaCl), and may be stored for several months in the cold in the presence of 0.1% NaNj. Any precipitate formed is removed by centrifugation and 6.0 ml 10% (w/v) dextran sulphate (Pharmacia) in TBS is added, under mixing. Excess of dextran sulphate is precipitated with 15 ml 1 M CaCl2. The precipitate is extracted with 50 ml TBS to recover any protein carried with the precipitate. IgY is then recovered from the combined supernatants by the method given in Section 

An alternative, simple method, with somewhat lower yield, is based on the aggregation of yolk lipid at neutral pH and low ionic strength. The yolk is diluted with 9 volumes of water and the pH is adjusted to 7.0 with 100 mM NaOH. After freezing and thawing, lipids are removed by centrifugation and IgY further purified from the supernatant as in Section 7.1.2.2. 

---