Modeling of complex antibody elution behavior under high protein load densities in ion exchange chromatography using an asymmetric activity coefficient. Issue 3 (9th February 2017) - Huuk, Thiemo C.
Abstract: A main requirement for the implementation of model‐based process development in industry is the capability of the model to predict high protein load densities. The frequently used steric mass action isotherm assumes a thermodynamically ideal system and, hence constant activity coefficients. In this manuscript, an industrial antibody purification problem under high load conditions is considered where this assumption does not hold. The high protein load densities, as commonly applied in industrial downstream processing, may lead to complex elution peak shapes. Using Mollerup's generalized ion‐exchange isotherm (GIEX), the observed elution peak shapes could be modeled. To this end, the GIEX isotherm introduced two additional parameters to approximate the asymmetric activity coefficient. The effects of these two parameters on the curvature of the adsorption isotherm and the resulting chromatogram are investigated. It could be shown that they can be determined by inverse peak fitting and conform with the mechanistic demands of model‐based process development. Abstract : The high load densities used in industrial ion‐exchange chromatography of proteins may lead to complex chromatogram shapes that cannot be modeled with the conventional Steric Mass Action (SMA) isotherm. Using a generalized ion‐exchange (GIEX) model, the experimentally observed strong adsorption at low load densities as well as the pronounced reaction to an increased salt concentration can be described.