(571c) A Mathematical Model for Protein Purification with Affinity Membranes

Affinity chromatography represents one of the most important and widely used unit operations in the biotechnology industry. However, bead-based columns suffer from several limitations such as high pressure drop, slow mass transfer through the diffusive pores and strong dependence of the binding capacity on flow rate. One possible alternative to overcome these drawbacks is represented by convective media columns packed with affinity membranes. In order to promote their application in large scale processes, it is imperative to develop a reliable simulation tool able to describe the process performance in a predictive way.

In this work we present a mathematical model for the purification of immunoglobulin G in columns packed with affinity membranes, and discuss the enhanced performance versus packed bead columns. Such chromatographic model is based on species mass balance equation over the convective medium, coupled with a suitable kinetic equation which represents the interaction between the IgG target molecule and the ligand immobilized on the porous support. A detailed analysis of the experimental data indicates that a bi-Langmuir binding kinetics is essential for a correct process description up to the saturation of the stationary phase.

The proposed model has been validated with experimental data obtained in chromatographic cycles performed with affinity membranes. The stationary phases studied derive from the functionalization of membranes with natural and synthetic affinity ligands that show high specificity towards IgG.

Model simulations are in good agreement with all of the experimental affinity cycles, demonstrating the accuracy of the model to describe the transport phenomena in the column and the adsorption binding mechanism.

The scale-up of the improved affinity materials for industrial applications is also addressed.