Green bioremediation of Brill Red 3BN dye using a bacterial consortium with phytotoxicity assessment for agricultural reuse

Azo dyes are extensively used in the textile industry, are known for their environmental persistence, toxicity, and resistance to conventional wastewater treatment. Bacterial dye degradation and detoxification at high concentrations under microaerophilic conditions remains largely unexplored. This study aimed to develop a novel bacterial consortium to degrade and detoxify high concentration of Brill Red 3BN (Acid Red 131) dye through an eco-friendly bioremediation approach. Two potent strains, Pseudomonas aeruginosa VITKSS5 and Klebsiella pneumoniae VITKSS6, exhibited strong biofilm formation and dye tolerance up to 50, 000 mg/L were screened for effective consortium development. This was the first to report 97.6% decolorization of 1,000 mg/L of Brill Red 3BN (BR-3BN) dye under microaerophilic conditions. FTIR analysis confirmed a several-fold reduction of functional groups such as C=O (carbonyl), C–H stretching, and aromatic bands indicate structural reduction of the synthetic dye. GC-MS spectra revealed a significant reduction of phenol, 3.5-bis(1,1-dimethylethyl) by 25.7% and benzene,(1-methylundecyl) by 17.2%, suggesting chromophore breakdown. Toxic phthalate derivatives like 1, 2-benzenedicarboxylic acid and dibutyl phthalate (endocrine disruptor) were reduced by 25.8% and 28.4%, respectively. Compared to untreated dye, bacterial treatment showed 61.3% reduction of overall phytotoxicity and enhanced root elongation in Lablab purpureus by 31.3%, likely due to the PGPR traits. The VITKSS5-VITKSS6 consortium demonstrated a promising solution for effective bioremediation of high concentration of BR-3BN dye. This study can contribute to the development of sustainable wastewater treatment technologies, following environmental clearance and ecological risk assessment. • VITKSS5 and VITKSS6 strains tolerated 50,000 mg/L dye concentration • Consortium achieved 97.6% decolorization of 1,000 mg/L Acid Red 131 dye • Phytotoxicity assays showed 61.3% reduction of overall toxicity • Effective detoxification of phthalate derivatives • Treated dye showed 31.3% enhanced root elongation in L. purpureus seeds