Efficient decolorization and detoxification of triarylmethane and azo dyes by porous-cross-linked enzyme aggregates of Pleurotus ostreatus laccase

Abstract

In this preset study, porous-cross-linked enzyme aggregates (CLEAs) of Pleurotus ostreatus laccase were utilized for the spontaneous decolorization and detoxification of triarylmethane and azo dyes, reactive blue 2 (RB) and malachite green (MG). The specific surface area and pore radius of the porous-CLEAs are 136.3 m2/g and 19.47 Ao, and the higher specific surface indicated greater biocatalytic efficiency, as increased mass transfer and dye interaction with the CLEAs laccase. CLEAs laccase decolorized 500 ppm of MG and RB with 98.12–58.33% efficiency after 120 min, at pH 5.0 and 50°C, without a mediator. Furthermore, the biotransformation of the MG and RB with immobilized laccase was confirmed with the help of UV–visible spectroscopy, high-performance liquid chromatography, and Fourier transform infrared spectroscopy. The reusability potential of CLEAs was assessed in batch mode for 10 cycles of dye decolorization. The decolorization activities for the immobilized laccase were 89% and 12% at the 6th cycle for MG and RB, respectively. This immobilized enzyme could effectively remove dyes from aqueous solution, and demonstrated significant detoxification in experimental plants (Triticum aestivum and Phaseolus mungo) and plant growth-promoting rhizobacteria (Azospirillum brasilense, Bacillus megaterium, Rhizobium leguminosarum, Bacillus subtilis, and Pseudomonas fluorescens). In conclusion, porous CLEAs laccase could be useful as a potential bioremediation tool for the detoxification and decolorization of dyeing wastewater in future.