Tyrosinase Immobilized Zein Nanofibrous Matrix as a Green and Recyclable Material for Biodegradation of Azo Dyes

The environment is currently affected by a wide range of contaminants and toxic chemical pollutants among which are the dyes present in industrial and textile wastewaters. Their removal from the textile effluents through enzymatic processes is considered one of the most environmentally friendly approaches among the available ones. In this pursuit, the partially purified tyrosinase enzyme was selected in this work to remove a toxic azo dye. The enzyme was immobilized on an electrospun zein nanofibrous matrix (ZNM) via glutaraldehyde crosslinking to enhance its activity, ease of separation, and reuse. The ZNM and zein nanofibrous matrix immobilized tyrosinase (ZNM-IT) were characterized by SEM and XRD analysis. The glutaraldehyde crosslinking with the matrix was confirmed by both FTIR and NMR spectroscopy. The relative activity of the free enzyme and the ZNM-IT were examined by activity assay. The decolorization and degradation efficiency of the ZNM-IT against various dyes were analyzed, also in binary mixture, by UV-vis spectroscopy and HPLC studies. The recycling study showed that the ZNM-IT completely degrades the tested dyes up to 5 cycles. The embryo toxicity of the dye solution treated with ZNM-IT was assessed on the embryos of Danio rerio and proved negligible. The treated binary dye mixture solution was mathematically modeled using response surface methodology. This work contributes valuable information to the knowledge on the degradation and biotransformation mechanism under optimal conditions, which has a great scope in dye removal from wastewater and the protection of the environment.