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

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.

Biodecolourisation of Reactive Red 120 as a Sole Carbon Source by a Bacterial Consortium—Toxicity Assessment and Statistical Optimisation

The application of microorganisms in azo dye remediation has gained significant attention, leading to various published studies reporting different methods for obtaining the best dye decolouriser. This paper investigates and compares the role of methods and media used in obtaining a bacterial consortium capable of decolourising azo dye as the sole carbon source, which is extremely rare to find. It was demonstrated that a prolonged acclimation under low substrate availability successfully isolated a novel consortium capable of utilising Reactive Red 120 dye as a sole carbon source in aerobic conditions. This consortium, known as JR3, consists of Pseudomonas aeruginosa strain MM01, Enterobacter sp. strain MM05 and Serratia marcescens strain MM06. Decolourised metabolites of consortium JR3 showed an improvement in mung bean’s seed germination and shoot and root length. One-factor-at-time optimisation characterisation showed maximal of 82.9% decolourisation at 0.7 g/L ammonium sulphate, pH 8, 35 °C, and RR120 concentrations of 200 ppm. Decolourisation modelling utilising response surface methodology (RSM) successfully improved decolourisation even more. RSM resulted in maximal decolourisation of 92.79% using 0.645 g/L ammonium sulphate, pH 8.29, 34.5 °C and 200 ppm RR120.