Extraction and purification of IgY

Abstract

Immunoglobulin Y (IgY) is an antibody present in the yolk of the egg and to obtain it at high purity levels, while retaining its biological activity, multi-step processes are required. The initial step is removal of the lipid fraction from the yolk. The delipidation methods routinely used are water dilution or precipitation by either polyethylene glycol (PEG), anionic polysaccharides or organic solvents. The second step is the extraction of the IgY from the remaining proteins in the mixture, which can be achieved by precipitation with a variety of salts, or additional PEG steps or by aqueous biphasic systems. The final step in IgY purification involves chromatographic methods based on different separation techniques such as cation exchange, hydrophobic charge-induction and various affinity systems giving IgY with 90% purity. In this chapter, comparisons among different methods of IgY extraction applied to a single batch of eggs and the commercial extraction kits currently available are discussed. Finally, the techniques for the characterization of the IgY with regard to purity and activity are outlined as well as the appropriate storage conditions.