Synthesis, characterization, and application of a poly(acrylic acid-co-acrylamide) cation exchanger (ACX) for camel...

The goal of this study is to develop an optimized poly(acrylic acid-co-acrylamide) cation exchanger (ACX) for protein purification. Cation exchange chromatography is a widely used technique in protein purification. ACX was synthesized and tailored to purify positively charged proteins using batch chromatography. ACX aims to reduce the overall cost of protein purification by integrating cheap monomers, tolerating unclean samples, and without grafting on expensive support materials. ACX was prepared as a copolymer of acrylic acid, acrylamide, and methylene-bis-acrylamide by the inverse emulsion polymerization technique. ACX was characterized by protein binding capacity, ion exchange capacity, elution behavior, pH titration, distribution studies, swelling properties, light microscopy, SEM, FTIR, TGA, and DTA. Then, it was challenged in the purification of lactoferrin -a positively charged protein- from raw camel milk. Microscopic examination of ACX verified the successful synthesis of spherical beads with a mean diameter of 141 ± 63 μm, which exhibited a protein binding capacity of 121.7 ± 0.58 mg/g of dry resin. Furthermore, the purification challenge with camel lactoferrin showed sufficient purity (93 %) with a high purification factor (145). While pH titration studies of ACX revealed its bifunctional nature, distribution studies showed its superior affinity to ferric ions. In conclusion, ACX offers an easy-to-fabricate and cost-effective alternative to commercial cation exchangers for the purification of positively charged proteins by batch chromatography.