Textile dye degradation potential of plant laccase significantly enhances upon augmentation with redox mediators

Abstract

Cell suspension cultures of Blumea malcolmii Hook. exhibited 98% decolorization of a textile dye Brilliant Blue R (BBR) at a concentration of 40 mg L⁻¹ within 24 h. A significant induction in the intracellular laccase activity (607%) was observed during decolorization of BBR. Twelve different redox mediators showed noteworthy degradation of BBR when added independently to cell cultures. Nevertheless, augmentation of 2,2′ azino-bis 3-ethylbenzothiazoline 6-sulfonic acid (ABTS) achieved 100% decolorization within 30 min. Purified laccase from B. malcolmii was revealed to have a molecular weight of 40 kDa. Thirteen different phenolic and non-phenolic substrates were also oxidized by the purified enzyme. The purified enzyme was found to degrade five structurally different textile dyes in the presence of ABTS. The enzyme took 12 h to completely remove BBR from the solution, however, addition of ABTS tuned up the catalytic action of the enzymes achieving up to 96% decolorization within 5 min. Degradation of BBR was confirmed by high performance liquid chromatography and gas chromatography-mass spectroscopy. The precise role of laccase in phytodegradation of BBR was further proposed in a schematic pathway. Phytotoxicity studies revealed a decrease in toxicity of degradation metabolites of the parent dye.