Isolation and Characterisation of Biofilm-Forming Thermophilic Bacteria for Congo Red Decolorization

In the present research, we isolate and characterize the thermophilic biofilm-forming bacteria of the textile industry that are responsible for the degradation of azo dye. The thermophilic bacteria that form biofilm grow at a temperature range of 45-80 ℃ and play an important role in bioremediation. Thermo-stable biofilm-producing bacteria are a unique class of microorganisms that flourish well in extreme environments. The study aims to screen and characterize thermophilic biofilm-producing bacteria isolated from the soil of the textile industry in Hindpiri, Ranchi, Jharkhand, India, to uncover their potential for Congo red decolorization. Two isolates, A1 and A2, which are able to form biofilm when grown in TSA, were used for further studies. After 3 days of incubation, maximum biofilm developed at 45 °C with pH 7-9. Biofilms were grown on glass coverslips and incubated with Congo red dye to evaluate their dye decolorization ability. Isolate A1 exhibited a high decolorization potential, 80% Congo red dye in 18 h, whereas isolate A2 had a lower efficiency, decolorizing only 60% of the dye under 45 ℃ at static conditions. 16S rRNA-based molecular characterization identified isolate A1 as Bacillus licheniformis A1 (PV362359). Analytical techniques like FESEM and FTIR analysis showed significant changes in bacterial cells and in functional groups, with a marked reduction or disappearance of peaks, respectively. Peaks at 1745 cm^-1, 2859 cm^-1, 2931 cm^-1, and 1154 cm^-1 give the alterations in protein and polysaccharides associated functional groups. These demonstrate the breakdown of the azo linkages and sulfonate groups. The present study indicates the potential of thermophilic biofilm-producing bacteria for azo-dye bioremediation.