Studies Of Adsorption Equilibrium And Kinetics Of Hydrophobic Charge Induction Chromatography

Hydrophobic charge induction chromatography (HCIC) is a novel bioseparation technique. The capture of target proteins can be achieved in a wide range of ionic strength without the need of dilution or other additives due to the high density and unique characteristics of its ligand. Thereby, the cost of purification can be significantly decreased. In hydrophobic charge induction chromatography (HCIC), proteins are adsorbed under hydrophobic intercation while elution is performed due to electrostatic repulsion at an acidic pH, at which the ligands on the hydrophobic surface are positively charged.The equilibria and intraparticle mass transfer of proteins in chromatography are of great importance for the design and optimization of bioseparation processes. However, the study and research of HCIC are still in the primary state with most of the work focused on screening and application of new ligands. Reseaches on the mechanism, the process theory and adsorption kinetics are still very few. Based on our previous work, theories of intraparticle mass transfer were studied in the thesis. The details in this work are summarized as follows.Firstly, Sepharose CL-6B was used as a medium to coupling new HCIC ligand after activated by epichlorohydrin with DMSO added to the reaction systerm. The density of epoxy groups reached 110μmol/g under the optimal condition. 5-amino indole was coupled to the medium and the ligand density can reach as high as 85μmol/g. Secondly, with lysozyme and bovine serium albumin (BSA) as model proteins, the isotherm adsorption behavior was investigated under different conditions. The results showed that the adsorption capacities increased with increasing ionic strength due to the stronger attraction between proteins and the adsorbent. However, the high density adsorbent showed an ability of salt-tolerate adsorption compared with the low density one. The elution of lysozyme was achived when pH decreased from 7 to 3, accorded with the mechanism of HCIC.Thirdly, the adsorption kinetics of lysozyme and BSA were studied in batch stirred flask and the effective diffusion coefficients were determined by fitting uptake curves with pore diffusion model. The results showed that the model could fit uptake curves of lysozyme and BSA well. The diffusivities of lysozyme were nearly the same in different ionic strengths while the ligand densities also had little influence. The behavior of BSA was different from lysozyme with the diffusivities decreased when the salt concentration was increased.The results reported in the thesis provided an insight into HCIC adsorption equilibria and kinetics of protein.