Studies Of Protein Adsorption Equilibrium And Kinetic Theories

Ion-exchange equilibria and intraparticle mass transfer of protein in chromatography are of great importance for the design and optimization of bioseparation processes. Compared with the extensive application of ion-exchange chromatography in biotechnology, the mechanism and process analysis of ion-exchange system are still in the primary state. The details in this work are summarized as follows.1. The adsorption equilibria of bovine serum albumin (BSA) and hemoglobin (Hb) to anion exchanger, DEAE Spherodex M, were studied by using statistical thermodynamic model (ST model). The ST model can well describe single and two-component protein equilibrium on the anion exchanger at different ionic strengths. The shielding effect of the co-ions in adsorption phase on the electrostatic interaction among protein molecules and adsorbents increases with an increase of ionic strength. At the same ionic strength, the electrostatic attraction between BSA molecules and DEAE Spherodex M is stronger, and the electrostatic repulsion among BSA molecules is stronger than that among Hb molecules. In two-component adsorption system, the electrostatic attraction between BSA molecules and adsorbent is stronger, BSA is more competitive. The effective protein charge values calculated respectively from ST model parameters 1/αiand k ii are consistent.2. The adsorption equilibria of BSA and Hb to cation exchanger, SP Sepharose FF, were also studied by using ST model. The shielding effect of the co-ions in adsorption phase on the electrostatic interaction among protein molecules and adsorbents increases with increasing ionic strength. Moreover, the electrostatic interaction among protein molecules and adsorbents decreases with increasing pH. At the same pH values and ionic strengths, the electrostatic attraction between Hb molecules and SP Sepharose FF is stronger, and the electrostatic repulsion among Hb molecules is stronger than that among BSA molecules. In two-component adsorption system, the electrostatic attraction between Hb molecules and adsorbents is stronger, so Hb is more competitive.3. The ion-exchange adsorption kinetics of BSA to the cation exchanger, SP Sepharose FF, was studied by batch adsorption experiments. Three diffusion models...