Concomitant mineralization and detoxification of acid red 88 by an indigenous acclimated mixed culture

Abstract

An indigenous mixed bacterial culture was screened and acclimated to decolorize a sulfonated azo dye; Acid Red 88 (AR88) under changing growth conditions. The process parameters influencing the average decolorization rate, ADRAR88 (μg min−1) was optimized using Taguchi's orthogonal array (OA‐L25), under design of experiments. The value of ADRAR88 is 888.86 (μg min−1) when the operational parameters like pH, 8.0, temperature, 35°C and AR88 concentration, 500 (mg L−1) were maintained for 6 h. The mixed culture exhibited 87.89 and 90.58% reduction in the level of chemical oxygen demand (COD) and aromatic amines, respectively. It was found that increasing AR88 concentration, were found to be insignificant on the basis of analysis of variance (ANOVA) and signal‐to‐noise ratio (SNR) variation for the obtained responses from Taguchi's OA experiments. The decolorization by the mixed culture was confirmed by UV–vis spectrophotometry, whereas biotransformation was evidenced by spectroscopic studies like Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H‐NMR), and chromatographic techniques like high performance liquid chromatography (HPLC), thin layer chromatography (TLC), and gas chromatography coupled with mass spectrometry (GC‐MS) analyses. The induction and activities of various AR88 degrading oxido‐reductive enzymes was elucidated. The phytotoxicity test using plant seeds revealed the extent of detoxification of parent dye compound by the mixed culture. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1455–1466, 2015