An Integrated Approach for Biodegradation of Toxic Azo Dyes and Wastewater Recycling by Azoreductase Gene–Harboring Bacillus paramycoides Strain AM-3

Treatment and recycling of textile effluents in an economical and eco-friendly manner is a global issue, especially in developing countries. The current study used an integration of wet and dry laboratory investigations to understand the significance of azoreductase enzyme in bacterial degradation of azo dyes and, subsequently, actual wastewater recycling. The study exclusively reports an indigenously isolated bacterial strain Bacillus paramycoides AM3 as an NADPH-dependent FMN reductase-harboring bacteria specifying 99.98% relatedness in the database based on the nucleotide sequence of its azoreductase enzyme. The RMSD values indicated the strong interaction of this enzyme with reactive black-5 (RB-5), reactive red-120 (RR-129), and Congo red (CR) dyes in molecular docking studies. In the wet laboratory experiments, approximately 80% of RB-5, RR-120, and CR were removed in 72 h by the strain AM-3, whereas yeast extract, pH 6, and 30°C turned out to be the best carbon source, pH, and temperature levels, respectively, to optimize dye degradation process for this strain. After treatment, the Bacillus paramycoides strain AM-3 lowered all standard water testing parameters such as pH, electrical conductivity, total suspended solids, total dissolved solids, chemical oxygen demand, and biological oxygen demand. In the pot experiment, the maize plants irrigated with recycled wastewater (treated with the strain AM-3) showed growth and metabolic response statistically at par with normally irrigated maize plants with distilled water, whereas the plants watered with non-treated wastewater revealed significantly less growth and physiological response. It was concluded that Bacillus paramycoides strain AM-3 is not only capable of degrading textile azo dyes but also treating textile effluents to the extent of their fitness for use in agriculture. Graphical Abstract: [Figure not available: see fulltext.].