Decolourisation And Biodegradation Of Textile Reactive Azo Dyes By A Strains Of Proteus Mirabilis

ABSTRACT

The discharge of coloured wastewaters into water-bodies has serious implications for the environmental and public health. Furthermore, the usual colour removal methods often result in aromatic amines which are toxic, mutagenic and carcinogenic. Developing a method that can both decolourise azo dyes and degrade the corresponding aromatic amines formed is expedient. In this study, the ability of newly isolated indigenous bacteria to decolourise textile/non-textile azo dyes and degrade the aromatic amines formed was investigated. An estimated 0.05 g of the organism was inoculated into triplicates flasks containing 100 ml of a simulated effluent prepared from reactive blue 13 (RB 13), reactive yellow 42 (RY 42) and reactive red 58 (RR 58). The effect of media, oxygen, pH and temperature on the decolourisation activity of an effective strain was also investigated. The formation of aromatic amines and the mineralization of same were investigated by subjecting the metabolites of RB 13 to UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR) and gas chromatography/ mass spectroscopy (GCMS) analyses. The enzyme systems responsible for the decolourisation/ biodegradation were also studied. Three of the fourteen bacterial strains isolated from various environmental sources showed >95 % decolourisation of the simulated effluent, within 24 hours. One of these effective strains, which has been identified as a stain of Proteus mirabilis using 16S rDNA, decolourised methyl red (a standard azo dye) effectively at optimal pH and temperature of 7 and 37OC respectively.