Efficient biocatalytic removal and algal detoxification of Direct Blue-15 by the hierarchically structured, high-performance, and recyclable laccase@yttrium phosphate hybrid nanostructures.

Abstract

From the environmental point of view, azo dye industrial effluent is a major public health concern due to its toxic, carcinogenic, and teratogenic characteristics. On the other hand, using enzyme-based technologies offers a promising systematic and controllable method for removing synthetic dyes from wastewater. In the present study, yttrium (Y3+) phosphate was applied for the synthesis of hybrid nanoparticles (HNPs) consisting of laccase as the green catalyst. When the association of HNPs was fixed by glutaraldehyde (GA), three-dimensional cubic structures with the regular arrangement were provided. GA increased the reusability of the fabricated hybrid nanostructures (HNSs) up to 32 successive cycles. About 85% of Direct Blue-15 was removed after a 4 h-treatment using laccase@YPO4•HNPs and laccase@GA@YPO4•HNSs. The azo dye removal data were well-fitted with a pseudo-second-order model for both types of the prepared HNSs. For the model freshwater green alga Raphidocelis subcapitata, the half maximal effective concentration (EC50) of the dye decreased 10- and 100-fold after the removal with laccase@YPO4•HNPs and laccase@GA@YPO4•HNSs, respectively. GA-treated HNSs (250 U L-1) inhibited the biofilm formation by approximately 78%, 82%, and 79% for Escherichia coli, Staphylococcus aureus, and Bacillus subtilis, respectively. Thus, the fabricated laccase@GA@YPO4•HNSs could be presented as a novel, efficient, and recyclable heterogeneous biocatalyst for wastewater treatment and clean-up.