Decolorization of amaranth <scp>RI</scp> and fast red <scp>E</scp> azo dyes by thermophilic <i>Geobacillus thermoleovorans</i><scp>KNG</scp> 112
Kotresh Kyathanahally Rajashekarappa, Gurumurthy Dummi Mahadevan, Shivayogeeswar Eshwarappa Neelagund, Madhuri Sathynarayana, Divya Vijaya, Sikandar I. Mulla
Abstract
Abstract BACKGROUND Accumulation of industrial dyes in wastewater creates not only environmental problems, but also medical and aesthetic problems. Removal of synthetic dyes from contaminated hot textile industrial discharge is a fundamental issue. Herein, the microbial decolorization of azo dyes amaranth RI and fast red E was studied. The decolorization process was studied in terms of various physicochemical and analytical parameters. RESULTS The azo dye decolorization efficiency was improved with beef extract and maltose as nitrogen and carbon sources, respectively. At 55 °C, Geobacillus thermoleovorans KNG 112 showed the maximum decolorization for both amaranth RI and fast red E at pH 7 and 8, respectively. Fourier transform infrared spectral analysis revealed the formation of amide, nitrosamine, aromatic and carbonyl compounds, alkyne, alkane, alcohol and alkyl halide groups after dye decolorization. Mixed dye (amaranth RI and fast red E) decolorization resulted in formation of various alkyl acetals, amines (nitrosamines, secondary and tertiary amines) azo groups and alkyl chloride. Furthermore, phytotoxic effect of azo dyes on the germination of fenugreek and green gram showed no inhibitory effects; however, more and rapid germination compared to the control group was observed. CONCLUSIONS The results lead to the conclusion that the optimization of G. thermoleovorans KNG 112 for removal of azo dyes could have applications in decontamination of hot industrial discharges. © 2021 Society of Chemical Industry (SCI).