Biodecolorization of Azo Dye Mixture (Remazol Brilliant Violet 5r and Reactive Red 120) by Indigenous Bacterial Consortium Obtained From Dye Contaminated Soil

Abstract Discharge of the untreated wastewater containing dyestuff into the surrounding aquatic environment is of significant environmental concern. These dying effluents not only change the color of water bodies but also has many unfavorable conditions and release toxic by-products, which are mutagenic, carcinogenic, and hazardous to different life forms. The present study investigated the biodegradation and removal of dye mixture (Remazol Brilliant violet 5R and Reactive Red 120) using a new bacterial consortium isolated from dye contaminated soil. Among the total 15 isolates screened, the two most efficient bacterial species (SS07 and SS09) were selected and identified as Enterobacter cloacae (MT573884) and Achromobacter pulmonis (MT573885) through biochemical assays and 16S rRNA gene sequencing. The removal efficiency of dye mixture by Enterobacter cloacae and Achromobacter pulmonis at an initial concentration of 100 mg L− 1 was 82.78 and 84.96%, discretely. The bacterial consortium was developed using selected isolates, and the optimum conditions for the removal of dyes were investigated by studying the effects of pH, temperature, carbon and nitrogen sources, dye concentration, and inoculum size. The maximum decolorization efficiency was achieved at pH, 7; temperature, 37°C; dye concentration, 100 ppm; and initial inoculum concentration, 0.5 ml, respectively. Mannitol and Ammonium sulfate was identified as the most suitable carbon and nitrogen sources for better bacterial growth and decolorization. The maximum removal efficiency of 91.3% achieved at the optimal conditions after 72 h of incubation. Decolorization of azo dyestuff by the developed microbial consortia conforms to the zero-order reaction kinetics model. Consortia of Enterobacter cloacae and Achromobacter pulmonis was established as an effective decolorizer for the Remazol Brilliant violet 5R and Reactive Red 120 dye mixture with > 90% color removal.