Azo Dye Decolorization under Microaerophilic Conditions by a Bacterial Mixture Isolated from Anthropogenic Dye‐Contaminated Soil

Abstract

Soil samples isolated from dye-contaminated sites were exploited for isolation of dye decolorizing microorganisms. A novel bacterial mixture, RkNb1, was selected based on its efficiency, showing maximum and faster decolorization of textile dyes. Seven bacterial strains were isolated and identified from the bacterial mixture as Ochrobactrum intermedium (HM480365), Ochrobactrum intermedium strain M16-10-4 (HM030758), Enterococcus faecalis (HM480367), Arthrobacter crystallopoietes (HM480368), Kocuria flavus (HM480369), Bacillus beijingensis (HM480370), and Citrobacter freundii (HM480371) by 16S rRNA gene sequence analysis. This bacterial mixture showed 98.17% decolorization of Reactive Violet 5 (400 mg L−1) within 8 h. The culture exhibited good decolorization ability at pH 8 and at a temperature of 37°C. Malt extract and peptone was found to enhance the decolorization rate of Reactive Violet 5. Plackett-Burman experimental design was used for elucidation of medium components affecting Reactive Violet 5 decolorization. Dye degradation products obtained during the course of decolorization were analyzed by high-performance thin-layer chromatography (HPTLC), Fourier transform infrared (FTIR), and nuclear magnetic resonance (NMR). The potential of this bacterial mixture to decolorize Reactive Violet 5 dye from manufacturing industry effluent is to be carried out using appropriate bioreactors.