Bioprospective decolourization of reactive azo dyes at pilot scale by a developed bacterial consortium using the RSM and CCD model

Textile industry effluent creates a negative impact to plants, animals and environment. The utilization of reactive azo dyes plays a colossal role in creating hazard to environment and water due to its toxic, carcinogenic and promote mutagenicity. The effective treatment of the effluent is mandatory to conserve nature and humans from critical risk. Microbial remediation is an eco-friendly method to degrade the dyes; specifically, bacterial consortium treatment is unique with reference to their mutual interaction. In this study, we have successfully developed an effective dye-decolourizing bacterial consortium and experimented to achieve the enhanced reactive dye decolourization in pilot scale. The culture characteristic factors influencing in bacterial consortium dye decolourization were further investigated and statistically optimised in response surface methodology (RSM) technique using central composite design (CCD) tool to maximize the decolourization process. Based on the antagonistic assay, the bacterial consortium design CD-3, consisting of Exiguobacterium aurantiacum TSL7, Bacillus firmus TSL9, and Brevibacillus laterosporus TS5 strains, demonstrated the highest RGY dye decolourization (83.78%) within 24 h. Bacterial consortium CD-3 productively decolourizes diverse dyes like magenta, yellow FG, and red (95%) in 24 h, followed by orange 3R (94%). The optimal concentration of selected factors for CD-3 dye decolourization is sodium chloride, yeast extract, initial dye concentration, inoculum size, and pH, which are 1.25%, 1.52%, 219 mg/l, 2.5%, and 6.5, respectively. The statistical analysis of tested factors, specifically dye concentration (carbon source), yeast extract (nitrogen source) and pH, has significant effects in process, and its mid-values have great influence in decolourizing results. Furthermore, the clear picture of the degraded non-toxic dye components was depicted by GC-MS result. Thus, the proposed biological treatment using bacterial consortium is effective one and can be used in the real world to address the pollution crisis.