Decolourization of azo dyes using immobilized bacterial isolates from termite mound ecosystem

Termites are one of the most abundant macroinvertebrates in the world having versatile roles in the ecosystem. The polymeric substances produced during the process of foraging and excretion of the termite ecosymbionts play major role in soil aggregation. In consequence, the termite ecosystem plays a vital role in improving soil health and nutrient. The present study investigates the potential bacteria isolated from termite mound soil that can decolourize synthetic dye. The result depicts that decolourization efficiency was 94.46, 91.64 and 89.67 per cent when Lysinibacillus fusiformis was cultured in the broth amended with congo red at 3 different concentrations say, 250, 500 and 1000 mg L⁻¹ respectively. Likewise, Mesobacillus jeotgali has an efficiency of 85.74, 82.04 and 79.27 per cent with methylene blue dye at 6 days after inoculation at dye concentrations of 250, 500 and 1000 mgL⁻¹ respectively. When immobilized cells Lysinibacillus fusiformis and Mesobacillus jeotgali were employed, the decolourization efficiency was found to be 96.04, 93.73 and 88.64 per cent with congo red and 91.56, 85.15 and 80.84 per cent with methylene blue respectively at 3 days after inoculation for dye concentrations 250, 500 and 1000 mg L⁻¹. Azoreductase activity was recorded highest of 0.089 units mg⁻¹ without immobilization and 0.093 units mg⁻¹ with immobilization. Subsequent FT-IR analysis showed that functional group modifications with Lysinibacillus fusiformis and Mesobacillus jeotgali was observed at 12 and 24 h after inoculation respectively.