Extraction and purification of IgG by hydrophilic organic solvent salting-out extraction

The distribution of IgG in different salting-out extraction systems (SOESs), including ethanol/K2HPO4, Na2CO3, and trisodium citrate, was investigated. The SOESs that were composed of 20% K2HPO4 (w/w)-14% ethanol (w/w), 19% Na2CO3 (w/w)-13% ethanol (w/w) and 25% trisodium citrate (w/w)-19% ethanol (w/w) showed satisfactory results, with IgG recovery rates as high as 97.4%, 93.1%, and 90.2%, respectively. ELISA, CD and IR analyses confirmed the active retention and structural constant of IgG in the K2HPO4-ethanol system. An optimized system that consisted of 14% ethanol (w/w)-20% K2HPO4 (w/w) (pH 7.0) was selected for extracting active plasma proteins directly from pig plasma. As a result, recovery rates as high as 95.7% for IgG and 93.0% for albumin were achieved. In addition, some contaminating proteins were also removed by this system, which may provide a new alternative method for the separation and purification of immunoglobulin.