Pleurotus ostreatus Laccase Decolorization of Remazol Brilliant Violet 5R Dye: Statistical Optimization and Toxicity Studies on Microbes and its Kinetics

Introduction: Nowadays, enzyme-based removal of hazardous dyes that pollute the environment has been considered as a substitute and eco-friendly method compared to the physical and chemical method. The present study was conceived in order to obtain the optimal condition for laccase-mediated (purified from the Pleurotus ostreatus PKN04) decolorization of Remazol Brilliant Violet 5R dye; a mono-azo dye, using the central composite design of response surface methodology (RSM). Materials and Methods: The design of experiment was suggested with 6 variables including pH, temperature, incubation time, agitation, dye concentration, and enzyme concentration, which were applied in order to optimize the decolorization process. The kinetic and energetic factors of laccases for the enzymatic removal of Remazol Brilliant Violet 5R dye was investigated. Results: Decolorization of Remazol Brilliant Violet 5R was maximally 95.72%, which had occurred at 6.0 pH, 40°C temperature, 60 minutes incubation time, 50 rpm agitation, 50 ppm dye concentration, and 100 IU/mL enzyme concentration. The obtained results of kinetic introduced the laccase-catalyzed decolorization of Remazol Brilliant Violet 5R as an endothermic reaction with Km and Vmax values of 0.801 mM and 387 mM/mg/min, respectively. In addition to the above results, the toxicity study against bacteria revealed that the toxicity of laccase-treated dye drastically reduced to the untreated dye. Conclusions: The results of the present analysis reveal that the Pleurotus ostreatus laccase is an efficient biocatalyst for decolorization of synthetic dye Remazol Brilliant Violet 5R dye.