Affinity adsorption of lysozyme with Reactive Red 120 modified magnetic chitosan microspheres

Reactive Red 120 was utilized as an affinity dye–ligand to modify the surface of magnetic chitosan microspheres to improve the adsorption capacity for lysozyme. The impact of pH, ionic strength, adsorption time and initial lysozyme concentration on the adsorption of lysozyme from aqueous solutions was investigated. An increased adsorption amount of 116.9 mg/g lysozyme on Reactive Red 120 modified microspheres was achieved in comparison to 24.6 mg/g on unmodified magnetic chitosan microspheres. The adsorption behaviour of lysozyme by the Reactive Red 120 modified magnetic chitosan microspheres fitted the pseudo second-order kinetic and the Langmuir thermodynamic model. The desorption ratio was 92.6% using 1 M NaCl phosphate buffer (pH 6.0) as the desorption agent. The adsorption capacity of the Reactive Red 120 modified magnetic chitosan microspheres did not decrease significantly after four adsorption–desorption cycles (P > 0.05). The as-prepared Reactive Red 120 modified magnetic chitosan microspheres were then used for the extraction of lysozyme from egg white solutions. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE) results showed that the purity of the obtained lysozyme was ∼80.7% and that the recovery yield was ∼89.1%.