Optimization of Reactive Blue 4 Decolorization by an Indigenous Bacterial Consortium of Acinetobacter sp. and Acidovorax sp. and Evaluation of Post-Treatment Toxicity Reduction

Abstract

Textile wastewater tainted with persistent synthetic dyes poses a severe ecological concern due to its resistance to conventional treatment methods and high toxicity. The present study was conducted to examine the biodegradation of Reactive Blue 4 (RB4), an anthraquinone dye, by a functional microbial consortium of two indigenous bacterial strains isolated from the textile effluent released from a small-scale textile industry in the Pilkhuwa industrial area of Hapur district, Uttar Pradesh, India. Twenty-three bacterial isolates were screened for their dyedecolourising potential, of which PI08 and PI20 exhibited the highest RB4 decolorization efficiencies of 96.8% and 95.7% respectively. Molecular identification based on 16S rRNA gene sequencing revealed the isolates as Acinetobacter sp. and Acidovorax sp. A compatible bacterial consortium was developed and evaluated for RB4 biodegradation. The effects of various operational parameters including pH, temperature, dye concentration and incubation conditions were optimized. Maximum decolorization (99.35%) was achieved at pH 7 while optimum temperature and dye concentration were found to be 35°C and 25 mg L⁻¹ respectively. Static incubation conditions were more favourable than shaking conditions, resulting in 99.05% decolorization. Under optimized conditions, the consortium achieved 99.6% RB4 removal within 72 h. Phytotoxicity assessment using Lens culinaris demonstrated significant toxicity reduction after biological treatment, with seed germination increasing from 73.3% in untreated dye solution to 95.6% in consortium-treated samples. The findings highlight the effectiveness of the developed bacterial consortium for RB4 biodegradation and suggest its potential application as an eco-friendly and sustainable strategy for the treatment of textile dye-contaminated wastewater.