Evaluation of protein-A chromatography media.

In process-scale antibody purification, protein-A affinity chromatography is commonly used as the initial purification step. In this paper, two different protein-A media were evaluated. These adsorbents have a porous glass backbone with different pore sizes: 700 A and 1000 A. Adsorption equilibrium data of human immunoglobulins on these media were measured via a batch technique and correlated using the Langmuir isotherm model. A larger static capacity was found for the smaller pore size material, which is probably a result of the larger specific surface area and associated higher ligand concentration. The protein uptake kinetics were also obtained via a stirred tank experiment using different initial protein concentrations. A surface layer model was used to represent the protein uptake by the media and to estimate values of a concentration-independent effective diffusivity within the particle. Experimental breakthrough curves were also obtained from packed beds operated under different conditions. Calculated breakthrough profiles were found to be in good agreement with the experimental results. Experimental breakthrough data were used to determine the dependence of the dynamic capacity of the media as a function of the fluid residence time. A larger dynamic capacity was also found for the smaller pore size media. The permeability of large scale packed beds was also reported and used in conjunction with the dynamic capacity to calculate the process production rate.