Preparation of uniform polyurea microspheres at high yield by precipitation polymerization and their use for laccase immobilization

Uniform polyurea (PU) microspheres were prepared using isophorone diisocyanate as the only monomer either in binary solvents of water/acetone (H 2 O/AT) or water/acetonitrile (H 2 O/AN), or in ternary solvent of H 2 O/AN/DMF, by precipitation polymerization without any shaking or stirring. Through careful examination, highly uniform microspheres were obtained at monomer concentration of 28.0 wt% at 65 °C in H 2 O/AN at 20/80 by mass, a value much higher than the previously (13.0 wt%) achieved in H 2 O/AT/DMF. The microspheres were analyzed by FTIR and NMR to confirm their PU structure and used as support for covalent immobilization of laccase via glutaraldehyde coupling. The immobilized laccase showed higher storage and thermal stability than the free laccase, and exhibited higher catalytic activity and better reusability in biodegradation of Congo Red and RBBR, compared with reported studies. In addition to enhancing the productivity of uniform microspheres, this study provides a new pathway to supported catalyst for enzymatic remediation of dyes-polluted water.