Purification of hen egg white ovomacroglobulin using one-step chromatography

Hen egg white (EW) are one of the most ideal sources of active proteins, and ovomacroglobulin, as a protease inhibitor, has been demonstrated to possess numerous biological properties including antibacterial and anti-inflammatory properties as well as activity for the treatment of keratitis. The objective of this study was to develop a simple and rapid method for the purification of ovomacroglobulin from hen EW on a laboratory scale. Hen EW was diluted with an equal volume of distilled water followed by a two-step PEG precipitation to remove ovomucin and to obtain ovomacroglobulin-rich precipitate. The precipitate was dissolved and further purified by gel filtration chromatography. Ovomacroglobulin was collected with a purity of 97.0 +/- 0.3% by HPLC and a yield of 62.5%. The atomic force microscopy images showed that ovomacroglobulin molecules on a mica surface emerged as an oval-shaped plate with a molecular volume of 1536.9 +/- 330.0 nm(3), indicating that purified ovomacroglobulin has an integrated molecular structure. With the improvement of PEG precipitation and the simplification of the chromatography, the whole purification process could be finished well within one working day. This protocol has an advantage of rapidity, and would facilitate studies of ovomacroglobulin.