Microbial Degradation and Detoxification of Synthetic Dye Mixture by Pseudomonas sp. SUK 1

Abstract

Textile industry is the major source of colored effluents constituting a number of complex dyes affecting terrestrial and aquatic ecosystems which necessitates their removal from environment. Bioremediation offers an inexpensive and eco-friendly approach hence, Pseudomonas sp. SUK 1, which is already known for its potential in degradation of individual dyes is used to degrade synthetic dye mixture of eight structurally different dyes. The bacterium was capable to remove 94.3 % American Dye Manufacturing Institute value of dyes mixture, within 24 h under static condition at pH 7 and 30 °C temperature. The results from the batch experiments revealed the ability of the tested bacterium to remove the synthetic dye mixture after repeated exposure. Induction in the activities of various biotransformation enzymes like laccase, veratryl alcohol oxidase, nicotinamide adenine dinucleotide-2, 6-dichlorophenol-indophenol reductase and tyrosinase was observed, indicating the significant role of these enzymes in biodegradation. After treatment significant decrease in chemical oxygen demand and biological oxygen demand was observed. The biotransformation of synthetic dye mixture was confirmed by UV–Vis spectroscopy, high performance liquid chromatography and Fourier transform infrared spectroscopy analyses of samples before and after decolorization. The toxicity analysis of degraded metabolites formed after biotransformation was carried out on Triticum aestivum, Phaseolus mungo and Sorghum vulgare crop plants with respect to germination ability, shoot and root length analysis. However oxidative stress study was carried out on Allium cepa L. proved that degraded metabolites were less toxic. Thus biodegradation of complex synthetic dye mixture to non-toxic metabolites using Pseudomonas sp. SUK 1 would be a better option for biological treatment of textile effluents.