Protein separation using plate-and-frame modules with ion-exchange membranes

The separation performance using plate-and-frame modules with ion-exchange membranes was investigated in this study. The proteins employed were lysozyme, BSA and γ-globulin. In the batch adsorption, the adsorption behaviors of lysozyme onto cation-exchange membranes and BSA onto anion-exchange membranes, both showing the heterogeneous adsorption, could be described more appropriately with the Suen model than the Langmuir model. In the flow process using a single plate-and-frame module, operating conditions greatly influenced the separation performance. At the elution stage, a better performance was achieved by using the cross-flow mode. Other operating conditions such as the number of membranes in a stack, the pH value at adsorption, and the mixed mode in the membrane stack also affected the separation performance. As to the two-module experiments, two different operation designs were tested: connection in tandem and connection in parallel. The tandem design resulted in a better protein recovery than the parallel design when only one kind of ion-exchange membrane was adopted. Regarding the mixed-mode effect in the tandem design, when the ion-exchange membranes suitable for the target protein were placed in the second module, the target protein could gain a longer time for adsorption and, hence, a better recovery was accomplished.