Spacer arm-facilitated tethering of laccase on magnetic polydopamine nanoparticles for efficient biocatalytic water treatment

Development of high performance biocatalysts generally seeks enhanced specific enzyme activities under intensified reaction conditions. This work reports a novel polydopamine fabricated Fe₃O₄ nanoparticles for incorporation with enzymes through the formation of flexible spacer arms using dialdehyde starch (DAS). It appeared that the biocompatible microenvironment and flexible tethering at the particle interface could effectively improve performance of the immobilized enzyme. In a test with laccase, such fabricated nanoparticles could reach enzyme loadings as high as 242 mg/g, while retained 69% specific enzyme activity. At the same time, the spacer arm-facilitated immobilization reduced the conformation changes with the control of interfacial action between enzyme and nanoparticles. Furthermore, the immobilized enzyme showed much improved stability against pH and thermal inactivation compared to free laccase. As a result, the immobilized laccase exhibited high degradation efficiency and reusability when tested for removal of 2,4-dichlorophenol and more contaminants from water. The results demonstrated a new strategy in fabricating nanomaterials using bio-based polymers for preparation of high performance biocatalysts.