Optimization and characterization of immobilized laccase on titanium dioxide nanostructure and its application in removal of Remazol Brilliant Blue R

Abstract

The objective of this study was to determine optimum condition for immobilizing laccase onto porous TiO 2 nanostructure, and to characterize the immobilized enzyme. XRD and FTIR analyses revealed that laccase was successfully immobilized. The maximum recovery activity of 85.30 ± 0.89% was achieved when immobilization conditions were: 1.5 mg/mL laccase concentration, pH 7.0, and 18 h contact time. Shifting of optimum temperature and pH were observed after immobilization. Kinetics revealed that the immobilized form had lower substrate specificity and catalytic rate compared to the free enzyme. Storage stability of the immobilized form were improved compared to the free enzyme. Interestingly, the immobilized laccase could preserve 31.84 ± 1.86% of enzyme activity after keeping the enzyme at room temperature continuously for 14 days. Maximum RBBR removal of 76.09 ± 0.47% was achieved at pH 5.0, and repeatability of the immobilized enzyme in decolorization was performed for 3 cycles with 40% decrease in efficiency. The immobilized laccase can be removed easily from the solution using forceps without further separation processes. • Combination of laccase enzyme and nanostructure was applied to produce the nanobiocatalyst. • Laccase was successfully immobilized on nano TiO 2 using covalent binding method. • Stability, durability, and reusability of the immobilized laccase were improved. • Maximum RBBR decolorization of the immobilized laccase was 76.09 ± 0.47% at pH 5.0. • After completion of the reaction, the immobilized laccase can be easily separated.