Biodegradation and decolorization of trypan blue azo dye by marine bacteria Vibrio sp. JM-17

Abstract

Marine microorganisms have shown the capability of azo dye degradation that is used in the textile and tanning industries and cause harmful environmental effects. In the present study, we isolated Vibrio sp. from the marine environment which decolorizes trypan blue dye (direct blue 14). The decolorization by Vibrio sp. was 90.33% in 6 day at 500 mg L−1 of dye concentration. The study of environmental parameters showed Vibrio sp. as well adapted bacterial isolate in trypan blue degradation and capable of decreasing dye load in industrial effluent. The high-performance liquid chromatography (HPLC) results showed a complete conversion of the major peak into the two new peaks. The formation of new peaks was further confirmed by functional group (SO, C–N, C–O, OH group) analysis by Fourier-transform infrared (FTIR) spectroscopy. The gas chromatography-mass spectrometry (GC-MS) showed less harmful small molecules i.e., the formation of by-products (alkane, alkene, fatty acid and benzene) after trypan blue dye degradation by bacterial isolate. Enzyme assay showed major involvement of azoreductase and tyrosinase in the degradation of trypan blue dye. In the proposed pathway, the decrease in toxicity of direct blue- 14 dye by destabilization of the di-azo bond and formation of the less harmful by-product as benzoic acid. The toxicity analysis of dye-degraded by-products (DDP) at different concentrations (1–25%) carried on seeds of Vigna radiata showed 100% of seed germination. Similarly, the toxicity of DDP at a 5% concentration was studied on edible seaweed Ulva lactuca which showed an increase in daily growth rate (DGR) with an increase in content of both chlorophyll a and chlorophyll b after 10 days of incubation. The results of the present study showed that bacterial isolate Vibrio sp. is capable of degradation of trypan blue dye with an environmentally friendly approach.