Eco-friendly degradation of methyl orange using Ralstonia pickettii

The widespread problem of dye pollution, with hazardous chemicals like methyl orange (MO) contaminating water sources, poses a significant threat to both the environment and human health. This study explored a promising and environmentally friendly solution: biodegradation of MO using the bacterium Ralstonia pickettii. The results demonstrated that R. pickettii effectively decolorized MO (100–200 mg/L) by 98 % under static conditions. The optimal conditions for decolorization were found to be a pH of 7 and a temperature of 40 °C. The decolorization of MO was maximized when the growth medium contained substrates like lactose broth, ammonium sulfate, urea, yeast extract, and gelatin. The culture exhibited significant decolorization capacity for 48 h. The activities of enzymes like laccase, NADH-DCIP reductase, and azoreductase suggest their involvement in breaking down MO structure. Metabolites formed after decolorization, including N, N-dimethylaniline (m/z 121), 4-amino-2,6-dihydroxybenzoate (m/z 169), and (2Z,4E)-5-amino-2,5-dihydroxypenta-2,4-dienoate (m/z 144), were characterized using FTIR and LC-TOF/MS. Phytotoxicity test showed the MO was toxic and metabolites obtained after its decolorization were nontoxic for the mungbean plant.