Decolorization and detoxification of sulphonated azo dye Red HE7B by Bacillus sp. VUS

Bacillus sp. VUS decolorized Red HE7B dye (100%) within 18 h in static anoxic conditions. A significant increase in activities of lignin peroxidase, laccase, NADH-DCIP and azo reductase was observed up to complete decolourization of RHE7B. The biodegradation was monitored by UV–Visible spectroscopy (UV–VIS), Fourier Transform Infrared (FTIR) spectroscopy and High Performance Liquid Chromatography (HPLC). The final products 4-methyl-3-(1-sulfo-ethyl)-5-([1,3,5] triazin-2-ylamino)-benzenesulfonic acid; 3-(1-sulfo-ethyl)-5-([1,3,5] triazin-2-ylamino)-benzenesulfonic acid and 3-(1,2-dihydro-[1,3,5] triazin-2-ylamino)-5-sulfomethyl-benzenesulfonic acid were characterized by gas chromatography–mass spectrometry (GC–MS). The phytotoxicity study revealed the non-toxic nature of the generated products with respect to Sorghum bicolor and Triticum aestivum. The metabolites produced after degradation increased the chlorophyll content of crop seedlings. The Ames test revealed the non-mutagenicity and non-carcinogenicity of the degraded products.