Laccase immobilized on magnetic nanoparticles modified by amino-functionalized ionic liquid via dialdehyde starch for phenolic compounds biodegradation

In this work, an efficient biocatalyst immobilized on magnetic nanoparticles modified by amino-functionalized ionic liquid using dialdehyde starch as cross-linker (Fe₃O₄-NIL-DAS) was fabricated. It was found that activity retention (73.7%), immobilization efficiency (85.8%) and storage stability (>80% of initial activity retained after 30 days) of laccase immobilized on Fe₃O₄-NIL-DAS (Fe₃O₄-NIL-DAS@lac) were improved significantly. Moreover, the immobilized laccase could effectively remove phenolic compounds (phenol, 4-chlorophenol and 2,4-dichlorophenol) in a wider temperature and pH range, exhibiting maximum removal efficiencies with 86.1%, 93.6% and 100% for phenol, 4-chlorophenol and 2,4-dichlorophenol, respectively, and high stability was confirmed by retention of 83.5% of the initial activity after six cycles. Fe₃O₄-NIL-DAS and Fe₃O₄-NIL-DAS@lac were characterized by transmission electron microscopy, energy dispersive spectrometer, zeta potential analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction analysis, magnetic hysteresis loops, circular dichroism and etc. Research results indicated that a novel and efficient strategy for enzyme immobilization to biodegrade phenolic compounds was developed.