Title: Bioremediation of synthetic dyes by Bacillus tropicus and Bacillus cereus isolated from a polluted site in Ogun State, Nigeria
Abstract:
The release of undesirable dye effluents from most textile industries into the environment constitutes a significant pollution load on the ecosystem. Dyes are recalcitrant to treat, and microbes’ propensity to effectively remove these pollutants and make the environment pollutant-free is pivotal. This work, under optimized conditions, investigated the decolourisation and degradative potential of two Bacillus strains isolated from contaminated soil, using molecular identification and phylogenetic tree analysis from 16S rDNA sequences. The UV-Visible and Fourier transform-infrared (FT-IR) spectroscopy were used to monitor decolourisation and biodegradative activities, respectively, in the bacterial strains. Bacillus tropicus strain OOA1 and Bacillus cereus strain OOA1 decolourized different dyes, with decolourisation not concentration-dependent but somewhat dye-type-dependent. However, the highest decolourisation, 88.90% and 67.70%, was observed for B. tropicus and B. cereus strain OOA, respectively, at the same concentration of 0.5mg/ml. FTIR identified cleavage of N=N bonds, cleavage of C=C, OH release, conversion of C−F to C–H groups and C=H bonds and cleavage of aromatic rings that showed biodegradation. The two strains exhibited azoreductase and laccase activities, indicating enzymatic reduction of azo bonds in the dye, which is key to their ability to bioremediate. Overall, the two isolates demonstrated appreciable effectiveness even at a high dye concentration of 1.0g/ml, suggesting they are probably well-suited for treating textile wastewater.
