In situ one-pot preparation of superparamagnetic hydrophilic porous microspheres for covalently immobilizing penicillin G acylase to synthesize amoxicillin

Abstract

Magnetic hydrophilic porous microspheres were successfully one-pot synthesized for the first time via in situ inverse suspension polymerization of glycidyl methacrylate, N,N′-methylene bisacrylamide and 2-hydroxyethyl methacrylate in the presence of Fe3+ and Fe2+ dispersed in formamide, which were denoted as magnetic Fe3O4-GMH microspheres. The morphology and properties of magnetic Fe3O4-GMH microspheres were characterized by SEM, VSM, XRD, FTIR, and so on. The formamide content had an important influence on the morphology of Fe3O4-GMH, and nearly perfectly spherical Fe3O4-GMH particles were formed when the amount of formamide was 15ml. The diameters of the microspheres were in the range of 100–200μm and Fe3O4-GMH exhibited superparamagnetic behavior with the saturation magnetization of 5.44emu/g. The specific surface area of microspheres was 138.7m2/g, the average pore diameter and pore volume were 15.1nm and 0.60cm3/g, respectively. The content of oxirane groups on Fe3O4-GMH was 0.40mmol/g. After penicillin G acylase (PGA) was covalently immobilized on Fe3O4-GMH microspheres, the catalytic performance for amoxicillin synthesis by 6-aminopenicillanic acid and d-hydroxyphenylglycine methyl ester was largely improved. As a result, 90.1% amoxicillin yield and 1.18 of the synthesis/hydrolysis (S/H) ratio were achieved on PGA/Fe3O4-GMH with ethylene glycol as solvent, but only 62.6% amoxicillin yield and 0.37 of the S/H ratio were obtained on free PGA under the same reaction conditions. Furthermore, the amoxicillin yield and S/H ratio were still kept at 88.2% and 1.06, respectively after the immobilized PGA was magnetically separated and recycled for 10 times, indicating that PGA/Fe3O4-GMH had a very good reusability.