Biodecolorization and biotransformation of methylene blue using mixed cultures of brown-rot fungus Daedalea dickinsii and filamentous fungus Aspergillus oryzae: identification of metabolites and degradation pathway

Abstract

This study aimed to examine biodecolorization and biotransformation of methylene blue (MB) using mixed cultures of brown-rot fungus Daedalea dickinsii and filamentous fungus Aspergillus oryzae. In addition, the ratio of D. dickinsii and A. oryzae in mixed cultures was 1 : 1, and the sample was incubated at 30 °C for 7 days in liquid medium potato dextrose broth (PDB). The results showed that the sample had the ability to remove and transform 95.24 mg L−1 MB. In this study, mixed cultures had the highest removal percentage of 64.77%, while values of 5.94% and 36.82% were obtained for single cultures of D. dickinsii and A. oryzae, respectively. LC-TOF/MS analysis results showed that peak intensity of MB compound (m/z 284) in each treatment chromatogram decreased compared to the control. The metabolites of decolorization by D. dickinsii were C15H16N3S, C16H19N3SO, and C16H21N3SO, while C31H48N3S+ was obtained using A. oryzae. For mixed cultures, the metabolites obtained included C26H37N2O3S, C9H8N2O3S, C28H38NO2S, and C27H27N5S2. Based on the results, mixed cultures of D. dickinsii and A. oryzae had a high MB decolorization and could be used in the textile industry.