Bio-inspired functional photocatalyst: Lipase enzyme functionalized TiO2 with excellent photocatalytic, enzymatic, and antimicrobial performance

Herein, we proposed a novel approach for the improvement of a photocatalytic material via functionalization with biocatalyst for successfully utilization in photocatalytic, enzymatic, and antimicrobial processes. For this, titanium dioxide (TiO2) was first modified using 3-aminopropyltriethoxysilane (APTES) to incorporate silane groups for the effective immobilization of Lipozyme TL 100 L enzyme. The as-synthesized samples were characterized by FT-IR, TGA, BET, SEM, XRD, XPS, UV–vis DRS and PL analyses in order to examine the thermal, structural, textural and optical features. The covalent immobilization yield of lipozyme on the modified TiO2 (TiO2@APTES) was found to be 97.5 % with 2,437.5 U/g of enzyme activity, and the immobilized enzyme (TiO2@LPZM) displayed excellent stability at different pH and temperatures when compared to its free form. The photocatalytic performance of TiO2@LPZM towards degradation of antibiotics significantly enhanced under both UV-A and visible light irradiation. The tetracycline and ciprofloxacin degradation rates of the bio-inspired photocatalyst were found 3.4- and 1.65-times higher than that of raw TiO2, respectively. The enhanced performance was ascribed to the attachment of target antibiotics by enzyme molecules, extended light absorption and reduced recombination rate of charge pairs. In addition, the enzyme immobilization increased the surface adsorbed oxygen species which boosted the photocatalytic reaction. The antimicrobial activity tests of the samples were examined against two types of bacterial species as E. coli and S. aureus and the enhanced antibacterial efficiencies were attributed to the presence of silanol, amino, and hydroxyl groups of modified TiO2. This research highlights the importance of enzyme immobilization on a photocatalytic support with synergistically improved surface features.