Research on superparamagnetic polyvinyl acetate microspheres for affinity separation of nattokinase

Micro-size magnetic polyvinyl acetate microspheres were prepared by a modification suspension polymerization, the magnetic beads were further modified with hydrolysis and aminization reactions, and magnetic affinity microspheres suitable for nattokinase purification were obtained by covalent immobilization of p-aminobenzamidine to the amino-modified magnetic beads by the glutaraldehyde method. The properties of magnetic beads were examined by SEM, XRD, FT-IR and VSM. The results showed that these magnetic beads were typically superparamagnetic and the specific saturation magnetization of ligand-attached magnetic beads was 32.4 emu/g. It took only 40 min to reach adsorption equilibrium and less than 15 min to achieve desorption equilibrium. The purification factor and the recovery rate of enzyme activity were 10.3 and 73.4%, respectively. The purified nattokinase gave a single sharp band on SDS PAGE.