Theoretical Studies Of Ion Exchange Equilibrium And Kinetics Of Protein

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 theory of ion-exchange system are still in the primary state. Theories of intraparticle mass transfer were studied in the thesis. The details in this work are summarized as follows.The adsorption equilibria of bovine serum albumin (BSA) to porous anion exchanger, Q-Sepharose FF, in different ionic strength and pH were studied by batch adsorption experiments. The results showed that the adsorption capacities of BSA decreased with an increase of ionic strength and a decrease in buffer pH whereas the dissociation constants increased. It is attributed to the electrostatic attraction between BSA and anion exchanger. The ion-exchange adsorption kinetics of BSA to the anion exchanger Q-Sepharose FF were studied in batch stirred cell. Three diffusion models, that is, pore diffusion, surface diffusion and parallel diffusion model, were discussed in our paper to analyze the mass transfer of BSA in the pore of matrix. The diffusion coefficients were determined by fitting uptake curves of BSA adsorption to Q-Sepharose FF in different conditions (e.g. ionic strength, pH). The result showed that all of diffusion models could fit uptake curves of BSA well. Increase in ionic strength and decrease in pH,the diffusivities of BSA to anion exchanger tend to increase in total. Although the main interaction between protein and ion exchanger is electrostatic interaction, there are still other interaction. The interactions between protein and ion exchanger were analyzed in details.The results reported in the thesis provided an insight into ion-exchange adsorption equilibria and kinetics of protein.