EFFECTS OF LIGAND CONCENTRATION ON PROTEIN ADSORPTION IN DYE LIGAND ADSORBENTS

The effect of ligand concentration on both equilibrium and fixed-bed adsorption has been studied for three model proteins on dye-ligand adsorbents. Adsorption equilibrium data corresponded well to the Langmuir isotherm. It was found that binding capacity was approximately proportional to immobilized dye concentration. Also it was observed that the more highly substituted adsorbents exhibited higher affinity for proteins. Breakthrough curves were measured for protein adsorption on fixed beds. These data were analyzed by a simple model to determine rate constants for the adsorption process. In general it was found that the rate constants decreased with increasing ligand concentration. The contributions of mass transfer and intrinsic adsorption kinetics to the overall rate were estimated, and it has been found that the adsorption kinetics are rate-limiting. The implications of these results on development of a dye-ligand process, as well as the validity and utility of this simple model for scale-up and design procedures, were discussed.