Fractionation of BSA and myoglobin with modified and unmodified ultrafiltration membranes.

Fractionation of the model proteins, bovine serum albumin and myoglobin, was studied with modified and unmodified polysulfone ultrafiltration membranes. A commercial polysulfone ultrafiltration membrane with a nominal cut-off value of 50,000 g mol-1 was used as the reference membrane, and it was modified with ultraviolet irradiation in different protein solutions. The permeate fluxes and the streaming potentials of the membranes were measured simultaneously. Ultrafiltration experiments were carried out at the isoelectric points of the proteins. The results show that the fractionation can best be carried out at the isoelectric point of myoglobin. Modification of the membranes with bovine serum albumin resulted in smaller adsorption and flux reduction, while membranes modified with myoglobin were more selective for myoglobin.