Preparation, structural characterization and enzymatic properties of alginate lyase immobilized on magnetic chitosan microspheres

Abstract

Abstract Alginate lyase is an enzyme that catalyzes the hydrolysis of alginate into alginate oligoalginates. To enhance enzyme stability and recovery, a facile strategy for alginate lyase immobilization was developed. The novel magnetic chitosan microspheres were synthesized and used as a carrier to immobilize alginate lyase. Immobilization of alginate lyase on magnetic chitosan microspheres was successful as proved by the Fourier transform infrared spectroscopy and X-ray diffraction spectra. The enzyme immobilization exhibited best performance at MCM dosage = 1.5 g/L, adsorption time = 2.0 h, glutaraldehyde concentration = 0.2%, and immobilization time = 2.0 h. The optimal pH of the free alginate lyase was 7.5, and this pH value was shifted to 8.0 after immobilization. No difference was observed in the optimal temperature (45°C) for the immobilized and free enzymes. The immobilized alginate lyase displayed superior thermal stability compared with the free alginate lyase. The Km of the free and immobilized enzymes were 0.05 mol/L and 0.09 mol/L, respectively. The immobilized alginate lyase retained 72% of its original activity after 10 batch reactions. This strategy was a promising method to immobilize alginate lyase.