A novel approach for high-resolution protein–protein separation by ultrafiltration using a dual-facilitating agent

This paper discusses a novel approach based on the use of the protein BSA as a dual-facilitating agent for manipulating the separation of two model proteins having comparable molecular weights. When a binary mixture of lysozyme and myoglobin alone was ultrafiltered, lysozyme was transmitted through the membrane to a substantially greater extent than myoglobin. However, when BSA was added to the feed solution, lysozyme was largely retained by the same membrane while the transmission of myoglobin was significantly increased leading to reversal of selectivity of separation. The decrease in lysozyme transmission was due to electrostatic BSA–lysozyme interaction, while the simultaneous increase in myoglobin transmission was due to Donnan effect. Thus, using a dual-facilitating agent the transmissions of lysozyme and myoglobin though a membrane could be manipulated as desired. This novel approach of using a dual-facilitating agent can be expected to significantly increase the flexibility of carrying out high-resolution protein–protein separation using ultrafiltration.