Adsorption of recombinant human erythropoietin and protein impurities on a multimodal chromatography membrane

Multimodal chromatography adsorbents are novel materials with promising properties for downstream processing of therapeutic glycoproteins. This work analyzes the properties of a salt-tolerant membrane, Sartobind STIC, for the purification of recombinant human erythropoietin (rhEPO) produced by human embryonic kidney cells. Batch adsorption experiments were carried out to determine equilibrium properties of the membrane as a function of pH and NaCl concentration. It was found that the membrane adsorbs strongly both rhEPO and impurity proteins but the selectivity of binding is low independent of process conditions. Since the membrane demonstrated strong salt tolerance, flow experiments were designed to elucidate the effect of elution conditions on the bound proteins desorption. These experiments have revealed irreversible character of protein adsorption on the multimodal adsorbent probably caused by protein unfolding on the hydrophobic groups of the adsorbent. The recovery degree was especially low in case of rhEPO with the maximum at about 45% even when solutions of kosmotropic agents were used as desorbents.