Lysozyme adsorption to cation exchanger derivatized by sequential modification of poly(ethylenimine)-Sepharose with succinic anhydride and ethanolamine: Effect of pH and ionic strength

Abstract In our previous work, a series of polyethylenimine (PEI)-derived cation exchangers were synthesized using PEI-grafted resin FF-PEI-L740 (ionic capacity, 740 mmol·L−1) as the basic resin to study lysozyme adsorption and chromatographic behavior. It was found that the resin with an ionic capacity of 630 mmol·L−1 (FF-PEI-CR630) possessed high adsorption performance towards lysozyme at 0–100 mmol·L−1 NaCl. Therefore, in this work, FF-PEI-CR630 was selected to study the influences of pH and ionic strength (IS) on protein adsorption and chromatographic behavior towards lysozyme. The increase of lysozyme adsorption capacity in the pH range of 6 to 10 was observed. However, the uptake rate decreased in the pH range of 6 to 8 and then remained essentially unchanged from pH 8 to pH 10. Increasing IS led to decreased protein capacity and increased uptake rate in different pH ranges. Besides, FF-PEI-CR630 maintained dynamic binding capacity as high as over 150 mg·ml−1 at pH 8–10 without NaCl. The research has thus provided insight into the selection of proper pH and IS conditions for protein purification using FF-PEI-CR630.