Indigenous Bacteria Synergistically Degrade Indigo Dye in Textile Wastewater via Enzymes and EPS

Abstract

Textile dye effluents pose a significant environmental concern due to their persistence, toxicity, and limited amenability to conventional treatment processes. Among these, indigo dye, widely used in denim manufacturing, is particularly resistant to degradation and contributes substantially to aquatic pollution. In this study, indigenous bacterial strains isolated from industrial effluents and contaminated soils were identified as Pseudomonas aeruginosa , Bacillus thuringiensis , and Bacillus cereus on the basis of 16S rRNA gene sequencing. Physicochemical analysis of the textile wastewater revealed pronounced alkalinity, high salinity, and a substantial organic load. Under optimized conditions, individual strains achieved up to 97% decolorization within 24 h, whereas the constructed consortium reached 99%, indicating a clear synergistic effect. Spectroscopic analyses (UV–Vis and FTIR), together with liquid chromatography (LC)–mass spectrometry (MS), confirmed the transformation of indigo into more polar metabolites, supporting biodegradation rather than simple adsorption. Mechanistically, dye removal appears to involve a coupled process of enzymatic oxidation (laccase and protease activity) and extracellular polymeric substances (EPS)‐mediated bioflocculation. The EPS matrix, dominated by proteins (P/C ≈ 1.98), likely enhanced pollutant capture and improved substrate accessibility, thereby increasing degradation efficiency. Importantly, validation in a 5 L fluidized bed bioreactor using real textile effluent demonstrated the robustness and scalability of the system. Overall, these findings underscore the promise of indigenous microbial consortia as effective, low‐cost, and environmentally sustainable solutions for textile wastewater treatment.