Sequential alginate grafting and sulfonation significantly improve the performance of alginate-grafted Sepharose FF for protein chromatography

Abstract

Alginate (Alg)-grafted Sepharose FF with an ionic capacity (IC) of 230 mmol/L (Alg-FF-230) was first prepared and then sulfonated to synthesize two cation exchangers of higher ICs (270 and 370 mmol/L, denoted as S-Alg-FF-IC). It was found that lysozyme adsorption capacity increased with increasing IC value, but the uptake rate (De/D0) on S-Alg-FF-370 was small (0.070) at 0 mmol/L NaCl because of the strong binding that limited surface diffusion of the bound protein. However, the dynamic binding capacity (DBC) of S-Alg-FF-370 was much higher in the salt concentration range of 0–150 mmol/L than the lower IC resins due to its high adsorption capacity and increased uptake rate. Especially at 150 mmol/L NaCl, the DBC of S-Alg-FF-370 was about 7.3 times higher than Alg-FF-230 and kept over 70 mg/mL at the flow rate up to 1350 cm/h. The results proved the high salt-tolerant feature of S-Alg-FF-370. By contrast, S-Alg-FF-270 showed higher DBC values than S-Alg-FF-370 in the same flow rate range at 50 mmol/L NaCl. Hence, S-Alg-FF-270 and S-Alg-FF-370 displayed different properties that would make them favorable for use in protein purification at different salt concentrations. The work thus proved that the sequential alginate grafting and sulfonation strategy is promising for creation of ion exchangers for high-performance and cost-effective purification of proteins from feedstocks of different ionic strengths.