Biodegradation of Textile Dyes by Radish Peroxidase (<i>Raphanus sativus</i> L.) Immobilized on Coconut Fiber

Abstract

The importance of biodegradation in the context of dye removal is presented as a function of the need to use enzyme immobilization as a key technology for effluent treatment. Immobilization is based on the need to improve the stability and recyclability of the biocatalyst in relation to the free enzyme, in addition to a lower risk of product contamination as an advantage. The present study aims to evaluate the biodegradation of textile dyes using radish peroxidase immobilized by physical adsorption method on coconut fiber, as well as its characterization in relation to pH, temperature, and infrared spectrum (FTIR). The discoloration efficiency (DE) of free radish peroxidase (FRP) and immobilized (IRP) on the dyes methylene blue (MB) and navy blue (NB) was determined by biodegradation assays conducted at 200 rpm for 1 h at 25°C. The evaluated parameters were: effect of pH, amount of biocatalyst (FRP for MB and NB; IRP for MB and NB), molar ratio dye: H₂O₂ (hydrogen peroxide) and contact time. Also, operational stability was analyzed. Under optimized conditions [pH 8.0 (MB) and pH 5.0 (NB), amount of biocatalyst to MB: 40.40 U (FRP) and 3.25 × 10⁻³ U (IRP), and to NB: 13.45 U (FRP) and 26.25 × 10⁻³ U (IRP), and molar ratio dye: H₂O₂ to IRP: MB (1:0.5 mmol/L) and NB (1:10 mmol/L)], the maximum DE for IRP was 86% for MB and 61% for NB. IRP can be reused ten times for MB and two times for NB. Thus, the results confirm the potential use of peroxidase of radish immobilized on coconut fiber in the biodegradation of dyes.