Optimization of parameters for decolorization of a textile azo dye, Remazol Black B (RBB) by a newly isolated bacterium, Bacillus thuringiensis BYJ1

Abstract

Bacillus thuringiensis BYJ1, a newly isolated bacterium from textile effluent contaminated soil was exploited to decolorize a textile azo dye, Remazol Black B (RBB). Various process parameters like initial RBB concentration, temperature, pH and cultural conditions on the process of dye decolorization were studied in order to determine optimum condition. Decolorization process was largely affected under aerobic process. Despite the toxic and inhibitory effects of dye, B. thuringiensis BYJ1 was able to tolerate as high as 1200 mg L-1 of RBB. Optimum decolorization of RBB was achieved at 37°C and pH 7 under static culture condition. Decolorization process was also studied using immobilized cells of B. thuringiensis BYJ1. The decolorized dye products were analyzed by thin layer chromatography (TLC), UV-visible scanning and fourier transform infrared spectroscopy (FTIR) analysis. Seed germination assay was performed to analyze the effect of decolorized dye products. The plasmid isolation and its curing from B. thuringiensis BYJ1 was performed to study effect of plasmid on the process of biodegradation of RBB. Key words: Azo dye, decolorization, immobilization, plasmid curing, Bacillus thuringiensis.