ISOELECTRIC PRECIPITATION OF BOVINE SERUM ALBUMIN AT THE PRESSURIZED CARBON DIOXIDE

摘要

A novel isoelectric precipitation technique for proteins in carbon dioxide-water-ethanol system, named Carbon Dioxide Isoelectric Precipitation (CO2 IP), was studied, where carbon dioxide was used as a volatile acid in the isoelectric precipitation and ethanol as an organic solvent in the conventional liquid antisolvent precipitation. This combination of two precipitations into one operation was favorable to precipitating some proteins. Here using BSA as a model protein, the precipitation process was investigated in detail. The solution pH in contacting of protein solution with pressurized carbon dioxide could be decreased to the isoelectric region of the model protein-BSA. Ethanol added into system would reduce the buffer capacity of system. Thus the protein concentration that could be precipitated went beyond the limits in system without ethanol, and well exploited the application field of the technique. In addition, owing to liquid antisolvent precipitation of ethanol, ethanol played a role of precipitation assistant in the process. The process was proved to make BSA little denaturation and inactivation by measuring the stability of BSA in the system.