Isolation, development and identification of salt-tolerant bacterial consortium from crude-oil-contaminated soil for degradation of di-azo dye Reactive Blue 220.

The objective of this study was development and characterization of a halophilic bacterial consortium for rapid decolorization and degradation of a wide range of dyes and their mixtures. The 16S rRNA gene analysis of developed halophilic consortium VN.1 showed that the bacterial consortium contained six bacterial strains, which were identified as Pseudomonas fluorescens HM480360, Enterobacter aerogenes HM480361, Shewanella sp. HM589853, Arthrobacter nicotianae HM480363, Bacillus beijingensis HM480362 and Pseudomonas aeruginosa JQ659549. Halophilic consortium VN.1 was able to decolorize up to 2,500 mg/L RB220 with >85% chemical oxygen demand (COD) reduction under static condition at 30 °C and pH 8.0 in the presence of 7% NaCl. VN.1 also exhibited more than 85% COD reduction with >25 mg/(L h) rate of decolorization in the case of different reactive dye mixtures. We propose the symmetric cleavage of RB220 using Fourier transform infrared, high-performance liquid chromatography (HPLC), nuclear magnetic resonance and gas chromatography-mass spectrometry analysis, and confirmed the formation of sodium-4-aminobenzenesulfonate, sodium-6-aminonepthalenesulfonate, and sodiumbenzene/nepthalenesulfonate. Toxicity studies confirm that the biodegraded products of RB220 effluent stimulate the growth of plants as well as the bacterial community responsible for soil fertility.