Abstract

Synthetic dyes like Congo Red (CR) are persistent pollutants in textile effluents, and conventional treatment methods often fail to achieve complete degradation. There is limited exploration of bacteria-mediated as well as bacterial polysaccharide-stabilised nanoparticles for rapid and sustainable azo dye bioremediation. Our present study explores an innovative bioremediation strategy for Congo Red (CR) decolourisation using a thermotolerant bacterium, Bacillus sp. DD5, isolated from textile industry effluent in West Bengal, India. The bacterium demonstrated high tolerance to CR (500 mg/L) and achieved 92.54% decolourisation of 200 mg/L CR within 24 h when supplemented with 5 g/L glucose. Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopy confirmed effective biodegradation with the breakdown of the azo bond and the absence of toxic aromatic amines. Additionally, a green synthesis approach was employed to generate bacteria-mediated palladium nanoparticles (PdNPs) using Bacillus sp. DD5, exhibiting 90.19% CR (200 mg/L CR) decolourisation within just 3 h under full-spectrum sunlight and H?O? treatment. Further, a cell wall polysaccharide (CPs5)–stabilised silver nanoparticle (AgNP) showed 78.08% decolourisation against the same concentration of CR under similar incubation conditions. From these results, it can be concluded that nanoparticle-mediated CR decolourisation is more efficient than other methods, as it requires less time while achieving higher degradation efficiency. These findings highlight the potential of bacterial biopolymers and green nanotechnology in sustainable wastewater treatment, offering an eco-friendly alternative to conventional dye remediation methods. Future studies should focus on scaling up this approach for industrial applications, assessing long-term environmental safety, and exploring the degradation of a broader range of synthetic dyes. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.