Commercial Blue Textile Dye Decolorization Using Aspergillus oryzae RH1 Isolated From Fermented Miso

The improper treatment of effluents from the textile industry is associated with severe health and environmental hazards. This study aimed to isolate and characterize miso-paste fungi that can decolorize commercial blue textile dyes (identified as Reactive Violet 5 [RV5] through spectral comparison). Response surface methodology (RSM) was employed to determine the optimal decolorization conditions, whereas molecular docking was performed to propose an enzymatic degradation mechanism. One colony, displaying the typical morphological characteristics of Aspergillus oryzae common in miso-paste starters, exhibited high decolorization potential for RV5. Validation of the RSM analysis using whole fungus A. oryzae RH1 revealed a decolorization performance of 92.33% under the following optimized conditions: 33 degrees C, pH 6.2, dye concentration of 200 ppm, and incubation period of 6 days. The optimal conditions for dye degradation via enzymatic catalysis, with peroxidase as the enzyme, were 51 degrees C and pH 3.0, resulting in a decolorization performance of 48.95% after 60 min of incubation. Molecular docking analysis suggested that the DyP-type peroxidase produced by A. oryzae RH1 can oxidize the azo bond, which is the chromophore group of RV5. In addition, biosorption was found to play a significant role in the decolorization of A. oryzae RH1. Altogether, these findings lay the basis for the use of A. oryzae RH1 in bioreactor systems for textile wastewater treatment.