Eco-friendly degradative decolourisation and detoxification of azo dye Amido Black 10B by Bacillus sp. strain AK1

In this study, an azo dye Amido Black 10B was decolourised and degraded by using bacterium Bacillus sp. strain AK1. The strain decolourised 96% of the dye in 30 h at 100 mg L-1 dye concentration. Decolourisation under different sets of conditions, such as increasing dye concentration (100-600 mg L-1), pH (5-11), temperature (25-55 degrees C) and salt levels (10-40 g L-1), was studied and found that the strain could decolourise up to 600 mg L-1 of the dye by about 54% in 72 h at pH 7 and 35 degrees C. The bacterium also exhibited the ability to act under varied pH from 5 to 11, temperature from 25 degrees C to 55 degrees C and salt levels of up to 30 g L-1. The azoreductase enzyme responsible for the breaking of azo bond exhibited the activity of 1.5371 mu M min(-1) mg(-1) protein. The products of dye degradation were identified by using UV-Visible spectroscopy and HPLC. The decolourisation also resulted in a decline in toxicity, as indicated by phytotoxicity assessment. There was also a corresponding decrease in the BOD and COD of the decolourised sample by more than 85%, which indicates the reduction in the pollution loads after decolourisation.