Evaluating the role of laccase immobilized TiO2 for potential use as biocathode in a microbial electrolysis cell

This research focused on evaluating the role of laccase oxide-reductase enzyme covalently immobilized on TiO2 nanoparticles for potential use as a biocathode. First, nanoparticles were functionalized with alkoxysilane molecules, followed by a reaction with glutaraldehyde, and finally, laccase was covalently immobilized. These materials were characterized by FTIR, zeta-potential, XPS, and SEM. Next, the enzyme-loaded nanoparticles were adsorbed on a glassy carbon (GCE) electrode for electrochemical characterization by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV). Findings revealed that the functional groups were attached, and laccase was immobilized in nanoparticles based on the analyses by FTIR, zeta-potential, XPS, and SEM-EDAX. Moreover, it was proven that laccase immobilized on TiO2 enhances the electrocatalytic activity when supported on a GCE; this bioelectrode exhibited a significant increase in oxidation and reduction current peaks compared to bare and TiO2-modified GCE. Also, the electron transfer rate was greatly improved for the laccase-based bioelectrode; the impedance magnitude of this bioelectrode was smaller than the corresponding GCE and GCE/TiO2 electrodes. Finally, polarization curves showed that the overpotential decreases and the cathodic current increases for the laccase-based electrode, indicating that it could perform well as a biocathode in a microbial electrolysis cell.