Abstract
Lysinibacillus sphaericus D3 cell-immobilized beads in natural gel sodium alginate decolorized the xylidine orange dye 1-(dimethylphenylazo)-2-naphthol-6-sulfonic acid sodium salt in the laboratory. Optimal conditions were selected for decolorization and the products formed were evaluated for toxicity by disc diffusion assay against common marine bacteria which revealed the non-toxic nature of the dye-degraded products. Decolorization of the brightly colored dye to colorless products was measured on an Ultra Violet-Vis spectrophotometer and its biodegradation products monitored on Thin Layer Chromatographic plate and High Performance Liquid Chromatography (HPLC). Finally, the metabolites formed in the decolorized medium were characterized by mass spectrometry. This analysis confirms the conversion of the parent molecule into lower molecular weight aromatic phenols and sulfonic acids as the final products of biotransformation. Based on the results, the probable degradation products of xylidine orange were naphthol, naphthylamine-6-sulfonic acid, 2-6-dihydroxynaphthalene, and bis-dinaphthylether. Thus, it may be concluded that the degradation pathway of the dye involved (a) reduction of its azo group by azoreductase enzyme (b) dimerization of the hydrazo compound followed by (c) degradation of monohydrazo as well as dimeric metabolites into low molecular weight aromatics. Finally, it may be worth exploring the possibility of commercially utilizing L. sphaericus D3 for industrial applications for treating large-scale dye waste water.
Highlights
With advances in analytical biotechnology, we are witnessing the birth of sophisticated analytical tools for the separation, characterization, and quantification of complex biological products
The information obtained from this study may be useful for further development of bacterium L. sphaericus D3 as a biocatalyst for the effective decolorization, degradation and detoxification of xylidine orange dye before its release into the environment
This is the first report on the efficient biotransformation of xylidine orange dye using L. sphaericus
Summary
With advances in analytical biotechnology, we are witnessing the birth of sophisticated analytical tools for the separation, characterization, and quantification of complex biological products. Dyes and pigments are extensively used as they play an essential role in the textile, leather, plastic and paper industry [1]. The color of the dye is imparted by the presence of chromophores like -N=N-,. The three most commonly used dyes are azo, anthraquinone and phthalocyanine [1]. In particular, contain an azo group (-N=N-) which usually links two aromatic systems or aromatic heterocycles or enolizable aliphatic groups [3]. As the demands for these products increases, dyeing wastewater increases several folds [4], and these dye industrial effluents pollute water bodies, causing unconditional pollution hazards to
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