An Application of Response Surface Methodology in Microbial Degradation of Azo Dye by <i>Bacillus subtillis</i> ETL-1979

Abstract

This research article deals with biodegradation of azo dyes by a newly isolated bacterial strain from activated sludge. Azo dyes are recalcitrant to the conventional modes of treatment due to their complex structure. This article reports decolorization of azo dye by, Bacillus subtillis ETL-1979. Response surface methodology was used to optimize the important physical parameters screened by Placket–Burman design. Five physical parameters such as pH, temperature (°C), dye concentration (mg/L), inoculum size % (v/v) and time (h) were tested by using Placket–Burman design criterion and all five parameters showed significant effect (P < 0.05) on decolorization of azo dye orange using Bacillus subtillis ETL-1979. The values of parameters was optimized by applying central composite design (CCD) and the most suitable values for orange dye decolorization by Bacillus subtillis ETL-1979, as predicted by the statistical tool, was pH 6.9; temperature 37.0°C; dye concentration 517 mg/L, inoculum size, v/v, (%) 5.5 % and time 23.7 h. At these optimum levels of parameters, bacterial decolorization of orange dye by 94.48% was obtained under static conditions. Biodegradation and decolorization of azo dye, orange, was confirmed using UV-VIS spectrophotometry, thin layer chromatography (TLC) and fourier transform infrared spectroscopy (FTIR) and electron spray ionization mass spectrometry (ESI-MS) analysis.