Degradation mechanism and toxicity reduction of methyl orange dye by a newly isolated bacterium Pseudomonas aeruginosa MZ520730

Methyl orange (MO) dye is recalcitrant in nature, hard to degrade and if released into the soil and aquatic resources could cause serious threats on environment and human health. MO is toxic to plant growth. Bacterial treatment may be a sustainable solution for its degradation and decolourization. In this work, a bacterium (RKS6) was isolated from textile industry wastewater and sludge samples and identified as Pseudomonas aeruginosa based on the 16S rRNA gene sequencing analysis. RKS6 showed more than 99% decolorization of MO dye (100 mg/l) and 96% reduction of total organic carbon (TOC) within 12 h, at 30 °C, pH 7 at static conditions. RKS6 also produced MnP enzyme of molecular weight ∼53 kDa as characterized by the SDS-PAGE analysis. Further, LC-MS analysis showed that MO dye was degraded into 4-[(4-aminophenyl) diazenyl] benzene sulfonate, 4, 2-((dihydroxymethyl) hyrazono-4) 5-benzene sulfonate, 4-(triazan-2-yl) benzene sulfonic, water and carbon dioxide by RKS6. Toxicity assessment showed that the solution treated by the bacterium allowed 90% seed germination indicating that RKS6 was effective in mineralization and detoxification of MO dye and can be effectively used in industrial wastewater treatment.