Biodegradation of Indigo Carmine Dye by Laccase from Bacillus licheniformis NS2324

Indigo carmine dye is used in many industries like textile, paper, cosmetics, etc. It is specially used in textile industries for dyeing denim. The untreated water discharged from these industries, especially the textile industry, poses a significant environmental threat. The conventional physicochemical methods used in treating industrial effluent are very expensive and cause secondary pollution. In the present study, an extracellular laccase-producing Bacillus licheniformis NS2324 was isolated, and a crude enzyme was used to degrade indigo carmine dye. The conditions needed for decolorisation were standardised. Optimisation studies for dye decolorisation by NS2324 laccase revealed that the enzyme was able to decolorize dye efficiently at 50 oC temperature, pH 8, with an enzyme dose of 10 IU/ml after 6 hours. Up to 96.79±1.06 per cent decolorisation was achieved under optimised conditions without the use of any mediator of laccase. Complete degradation of indigo dye by laccase in the absence of mediator makes the present study very useful for treating textile effluent from the denim industry.