Decolorization and Detoxification of Synthetic Dye-Enriched Simulated Wastewater by a Newly Isolated Bacillus licheniformis Strain WLS

Abstract

The present study investigates a newly isolated bacterial strain from wood-rot soil for its capacity to decolorize simulated wastewater containing a complex mixture of textile dyes. The biodegradation of the dyes was also explored, and the toxicity of both treated and untreated wastewater was assessed using phytotoxicity assay. The organism was identified as Bacillus licheniformis based on 16S rDNA sequencing. Decolorization was monitored using UV–Vis spectroscopy, and biodegradation was confirmed through FTIR and GC–MS analyses. Detoxification was further established by phytotoxicity assay. The organism effectively decolorized the simulated wastewater within 24 h, achieving decolorization efficiencies of 93% and 96% with dye concentration of 50 mg/L and 250 mg/L respectively. FTIR bands in the range of 802–775 cm⁻¹ and the peak at 1753 cm⁻¹, which are in the fingerprint region and are characteristic of C–H bending in substituted aromatic rings, were observed in the spectrum of the simulated wastewater but were absent in the spectrum of the metabolites. A similar observation was made for the peak at 1585 cm⁻¹, corresponding to in-ring C=C stretching. Remarkable variations were also noted in the fragmentation patterns of the GC–MS spectra and in the peaks of the GC chromatogram of the metabolites compared to those of the simulated wastewater. The decolorized wastewater supported germination of Zea mays (100%) and Vigna unguiculata (86.67%), but these rates were reduced by 13.3% and 6.67%, respectively, in seeds exposed to the untreated simulated wastewater. Overall, Bacillus licheniformis strain WLS demonstrated effective biotransformation of dye-enriched simulated wastewater by degrading its constituent dyes and converting them into less toxic metabolites, highlighting its potential for the bioremediation of dye-laden effluents.