Evaluating the efficacy of bacterial consortium for decolorization of diazo dye mixture

Textile wastewater contains dyes mixed with other contaminants in various concentrations. Bacteria-mediated decolorization and degradation of azo dyes have achieved momentum as a method of treatment attributed to their inexpensive, eco-friendly, and application to a wide range of azo dyes. However, a single species of bacteria is inefficient in decolorizing diverse groups of dyes which is one of the most significant challenges for environmental technologists working in bioremediation. In the present study, an aerobic bacterial consortium AUJ consisting of six different bacterial strains (Pseudomonas stutzeri AK1, Pseudomonas stutzeri AK2, Pseudomonas stutzeri AK3, Bacillus spp. AK4, Pseudomonas stutzeri AK5, and Pseudomonas stutzeri AK6) removed the individual azo dyes in the 24-94% range when used in more than 200 ppm concentration within 72-96 h. In addition, the consortium was able to decolorize 52.19% mixed dyes (100 ppm) and 44.55% Acid blue 113 when used at a concentration as high as 1100 ppm within 96 h. Optimization of various nutritional and environmental parameters revealed that glucose and yeast extract were the preferred carbon and nitrogen source, respectively, and analysis of treated dye products using high-performance liquid chromatography (HPLC), Fourier-transform infrared spectroscopy (FTIR), and gas chromatography-mass spectrometry (GC-MS) confirmed the breakdown of dye. In all, we present a bacterial consortium with a good ability of dye decolorization that can be used for degrading a wide variety of azo dyes.