Biotransformation of Reactive Orange 16 by alkaliphilic bacterium Bacillus flexus VITSP6 and toxicity assessment of biotransformed metabolites
Azo dyes are the largest group of chemically synthesized colorants used in various industries. The hazardous nature of these dyes has led to the development of stringent environmental laws. Thus, mounting pressure exists on the industries for development of cost-effective dye removal systems. The current work focuses on the bioremoval of azo dye Reactive Orange 16 (RO-16) using indigenous bacteria isolated from contaminated sample of a textile industry. The most potent bacterium was capable of decolorizing 89.82% of RO-16 within 24 h under static conditions and was identified as Bacillus flexus VITSP6. When physicochemical parameters were optimized, B. flexus VITSP6 showed efficient decolorization at a temperature of 37 °C, pH 11, glucose as carbon source and peptone as nitrogen source. Interestingly, although B. flexus VITSP6 showed highest decolorization at 37 °C, it was able to maintain its decolorization potency even at elevated temperatures as high as 52 °C. Further the mechanism of dye decolorization was deduced with the help of high-performance liquid chromatography, Fourier transform infrared spectroscopy and liquid chromatography mass spectrometry analyses. These analyses revealed that RO-16 underwent biotransformation to different lower molecular weight aromatic compounds. The toxicity of these biotransformation products were evaluated by conducting phytotoxicity, cytotoxicity and biotoxicity assays. All the toxicity assays indicated that the biotransformed products were non-toxic in nature. The efficient dye decolorization property of B. flexus VITSP6 and its ability to withstand high temperature and alkaliphilic nature make it a highly potential organism to be applied in the dye removal treatments.
KeywordsAzo dye Biotransformation Decolorization Reactive Orange 16 Toxicity assay
The authors of this paper wish to thank VIT management for providing a suitable platform to carry out this research work and also CSIR-CLRI for providing with LC–MS service.
Compliance with ethical standards
Conflict of interest
The authors of this paper declare that they have no conflict of interest in the context of this research paper submitted to the journal.
This article does not contain any studies with human participants. However, invertebrate (Artemia salina) eggs used for lethality assay in this study do not require any ethical committee clearance certificate for usage.
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