Fractionation Characteristics of Binary Protein Mixtures by Ultrafiltration

Ultrafiltration (UF) of mixtures of bovine serum albumin (BSA) and egg white lysozyme was conducted using membranes which were almost completely retentive for BSA but permeable for lysozyme. The experimental data have clearly demonstrated that the separation properties of binary protein mixtures are largely influenced by the hydrodynamics above the membrane, the solution environment, and the adsorption of the protein solutes within the membrane. In particular, it must be noted that the increase of the shear stress acting on the membrane surface improves the filtration rate, but causes the increase of the lysozyme rejection, resulting in a reduction in the fractionation efficiency. Furthermore, the effects of ultrasonic irradiation on the UF properties have been tested experimentally. Although the filtration rate was enhanced significantly by ultrasonic irradiation, the lysozyme rejection remained unchanged. The results showed that ultrasonic irradiation is quite effective for protein fractionation.