Reversible immobilization of glucoamylase by metal affinity adsorption on magnetic chelator particles

Magnetic Cu2+-chelated particles, prepared by cerium initiated graft polymerization of tentacle-type polymer chains with iminodiacetic acid (IDA) as chelating ligand, were employed for glucoamylase immobilization. The particles had an obvious high adsorption capacity of glucoamylase with a great activity recovery of 84.0% after immobilization. The immobilized glucoamylase exhibited improved stability in reaction conditions over a wide pH region (pH 3.5–6.0) and a broad temperature range (45–75 °C). The value of the Michaelis constant (Km) of the immobilized glucoamylase (1.77 mg/ml) was higher than that of the free one (1.07 mg/ml), whereas the maximum velocity (Vmax) was lower for the adsorbed glucoamylase. Storage stability and temperature endurance of the immobilized glucoamylase were found to increase greatly, and the immobilized glucoamylase retained 75.7% of its initial activity after 30 successive batch reactions. The magnetic Cu2+-chelated particles also exhibited excellent reusability, indicating the advantage of the magnetic metal-chelated particles in biocatalytic applications.