β-Agarase immobilized on tannic acid-modified Fe3O4 nanoparticles for efficient preparation of bioactive neoagaro-oligosaccharide

beta-Agarase was immobilized by using tannic acid modified-Fe3O4 magnetic nanoparticles (TA-MNPs) as a support material. The MNPs were synthesized by improved chemical coprecipitation method and modified with TA for agarase immobilization. TA-MNPs and immobilized beta-agarase were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA), all of which indicated the successful surface modification of MNPs with TA and the immobilization of beta-agarase. The optimal immobilization conditions for 25 mg TA-MNPs included 100 r/min oscillation speed, immobilization time of 2 h, immobilization temperature of 15 degrees C, and initial beta-agarase concentration of 3 mL (480 U). Immobilized beta-agarase showed better pH and thermal stability and excellent reusability than the free enzyme. Results revealed the promising application of beta-agarase-TA-MNPs for the preparation of neoagaro-oligosaccharides with different average polymerization degrees and varying activities in the antioxidant.