Eco-sustainable bioremediation of industrial azodye micropollutants by extremophilic plant growth promoting bacterium Halomonas desertis G11

Abstract

Application of extremophilic plant growth promoting bacteria (PGPB) and their enzymes in bioremediation have been received increasing interest due to their eco-friendly nature and effectiveness for bio treatment of diverse industrial micro pollutants. In this work, the azo-dye decolorization potential of halophilic PGPB Halomonas desertis G11 was evaluated and optimized using central composite experimental design and response surface methodology. Interestingly, the increase of pH and NaCl concentration accelerated the dye decolorization. The model predicted a maximum removal of BEZACTIV blue S-2G dye (80%) at optimal operating conditions (dye concentration of 50 mg/L, inoculum size of 1.0%, pH of 8.2, NaCl of 5.0% and incubation time of 10 days). The experimental design model predictions are in good agreement with the experimental data, thereby providing the soundness of the developed model. The biodecolorization under pressures of high salinity and alkalinity seems to be correlated to azoreductase activity. The gene encoding FMN-dependent NADH azo-reductase from halophilic bacterium H. desertis G11 was identified and the structure and catalytic mechanism of dye decolorizing enzyme were elucidated. Results of this study provide evidence for the potential application of this azoreductase producing extremophilic bacterium as a novel candidate in the biological treatment of sediments and wastewaters contaminated by azo-dyes.