DNA directed immobilization of horseradish peroxidase on phase- transitioned lysozyme modified TiO2 for efficient degradation of phenol in wastewater

Abstract

In this work, TiO2 nano particle was used for two purposes: it played as a role of a solid carrier for immobilization of HRP, and meanwhile acted as a photo-catalyst itself. In this way, the loss of enzymatic activity during enzyme immobilization can be compensated by the coupling of TiO2 photo-catalysis. Then, the surface of TiO2 nanoparticles were modified by phase-transitioned lysozyme (PTL) and connected with horseradish peroxidase (HRP) via a DNA helix (HRP-DNA-PTL@TiO2). The DNA double helix chain was utilized as a flexible spacer arm to keep the flexibility of the immobilized enzyme. The HRP-DNA-PTL@TiO2 showed a high recovered activity (90.52%) of the original activity of free HRP. This data is better than most reported activity recovery of immobilized enzyme. Moreover, HRP-DNA-PTL@TiO2 can maintain high catalytic activity, stability and reusability when degrading phenol in wastewater. The phenol of 0.5 mmol∙L−1 could be totally degraded within 10 min. Moreover, a visual colorimetric method for phenol concentration by HRP-DNA-PTL@TiO2 was established, and the phenol concentration of 0–0.2 mmol∙L−1 can be visually detected with naked eyes. Furthermore, an enzymatic-photocatalytic synergetic effect of HRP-DNA-PTL@TiO2 is found and investigated. The efficiency of HRP-DNA-PTL@TiO2 ensures it a potential application in the wastewater treatment.