A novel dialysis process to isolate phosvitin from hen egg yolk

The objective of this work is to develop a novel dialysis process for the isolation of phosvitin from hen egg yolk avoiding the use of organic solvents and polyvalent metals. This bioseparation process consists of NaCl precipitation, heat treatment and dialysis, which was proposed on the basis of the property difference (especially solubility and thermostability) among yolk proteins. The native molecular mass of the purified phosvitin estimated by fast protein liquid chromatography on a Superdex 75 column was about 165 kDa. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed two bands around 35 kDa. The nitrogen to phosphorus atomic ratio of the purified phosvitin was 2.8 +/- 0.2, with a yield of 87.1%. The phosvitin product had a-helix of 36%, beta-sheet of 28% and random coil of 36% at pH 7.0, consistent with the literature values. This shows that the purified phosvitin folded with a reasonable secondary structure.