Response surface methodology mediated optimization of Indanthrene Blue RS by a novel isolated bacterial strain Bacillus flexus TS8.

The enhanced decolorization and detoxification of Indanthrene Blue RS dye, under aerobic conditions, by a novel isolated anthraquinone-degrading bacterium, Bacillus flexus TS8, has been presented in this paper. The optimal decolorization conditions were determined by response surface methodology based on Box-Behnken design. The results indicated that the strain TS8 possessed the highest decolorization efficacy at pH 10.26, temperature 30.97 ºC and an inoculum size of 10.48% (v/v). It also revealed that about 98.01% of 100 mg/L of Indanthrene Blue RS could be decolorized within 24 hr under these optimized conditions. The subsequent degradation of the dye and the formation of metabolites were studied using analytical techniques such as UV-Vis spectroscopy, FTIR, and ESI/LC-MS analysis. The UV-Vis analysis of the colorless bacterial cells demonstrated that Bacillus sp. TS8 possessed this decolorizing activity through biodegradation. The degraded products obtained from ESI/LC-MS analysis were identified as 1-hydroxyanthracene-9, 10-dione (m/z-224), 1, 4-di-hydroxyanthracene-9, 10-dione (m/z-240), and phthalic acid (m/z-168). This study investigated the highest decolorization efficacy of strain TS8 to be utilized in the biological treatment of wastewaters containing anthraquinone dyes. PRACTITIONER POINTS: Enhanced decolorization of anthraquinone dye wastewater. Ninety-eight percentage of dye decolorization was obtained within 24 hr. Optimization of process parameters through the response surface methodology. ESI/LC-MS analysis identified phthalic acid as the end product of Indanthrene Blue RS degradation. Degradation pathway for Indanthrene Blue RS is outlined.