A dye-decolorizing bacterium was isolated from a soil sample and identified as Bacillus thuringiensis using 16S rRNA sequencing. The bacterium was able to decolorize three different textile dyes, namely, Reactive blue 13, Reactive red 58, and Reactive yellow 42, and a real dyehouse effluent up to 80-95% within 6 h. Some non-textile industrially important dyes were also decolorized to different extents. Fourier transform infrared spectroscopy and gas chromatography-mass spectrometer analysis of the ethyl acetate extract of Congo red dye and its metabolites showed that the bacterium could degrade it by the asymmetric cleavage of the azo bonds to yield sodium (4- amino-3-diazenylnaphthalene-1-sulfonate) and phenylbenzene. Sodium (4-amino-3-diazenylnaphthalene-1-sulfonate) was further oxidized by the ortho-cleavage pathway to yield 2- (1-amino-2-diazenyl-2-formylvinyl) benzoic acid. There was induction of the activities of laccase and azoreductase during the decolorization of Congo red, which suggests their probable role in the biodegradation. B. thuringiensis was found to be versatile and could be used for industrial effluent biodegradation.
The sorption capacity of untreated and alkaline-treated coconut shaft biosorbents for the removal of Pb 2+ from aqueous solution was investigated in batch experiments. Effects of contact time, biosorbent dose, initial metal concentration, and pH on the sorption capacity were investigated. Optimum Pb 2+ removal of 17.6 and 22.1 mg/g by untreated and alkaline-treated biomass was achieved at an initial metal concentration of 150 mg/L, a biomass dose of 0.7 g, a contact time of 80 min, and a pH of 4.0. The sorption data fitted well into the Langmuir isotherm, while kinetic modeling of the data from untreated biomass indicated conformity with the Lagergren pseudo-first-order model, whereas data from the treated biomass fit well with the Elovich model. FT-IR results gave indications of possible functional groups on the cell walls of the coconut shaft, including alcohols, amines, carboxylic acids, ester, and ethers. Thus, alkaline treatment of the coconut shafts enhanced the biosorption ability of Pb 2+ onto the coconut shaft biomass.
Developing efficient, effective and low-cost procedure for color removal in wastewater is a serious environmental concern. In this study, we investigated the possibility of enhancing the activities of dyes decolorizing bacterium using selected redox mediators and media (nutrient broth, yeast, glucose, starch and peptone). The isolated organism identified using 16S rRNA gene as Providencia rettgeri showed the highest decolorization of a model dye, methyl red by 97% within 6 h using nutrient broth. Preferred redox mediator was found to be quinol (95% within 5 h) than other (nicotinamide adenine dinucleotide (NAD + ), reduced NAD + , nicotinamide adenine dinucleotide phosphate (NADP + ) and reduced NADP + ). In addition, the biodegradation of methyl red was investigated by subjecting its metabolites to UV-visible, highperformance liquid chromatography and Fourier transform infrared analyses that suggested the biodegradation. This was confirmed by the removal of signature peaks of aromatic C-H bending (645, 759 and 831 cm −1 ) and the N=N peak at 1509 cm −1 of the FTIR spectrum of the metabolites. In conclusion, introduction of minute amount of hydroquinone (1 mM) into wastewaters could enhance their biotreatment by this strain of P. rettgeri.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.