Dyes are the most challenging pollutants for the aquatic environment that are not only toxic, but also interfering photosynthesis as light penetration into deep water is changed. A number of methods are used for the water reclamation, however, among them biological methods are preferably used due to their compatibility with nature. In the present research, 15 different bacterial strains were used to decolorize Brown 706 dye. Among the bacterial strains, Pseudomonas aeruginosa showed maximum decolorization activity; hence in the subsequent experiments Pseudomonas aeruginosa was used. First the decolorization activities were carried out under different physicochemical conditions to obtain the optimum decolorization benefits of the selected microorganism. The optimum conditions established were 37°C, pH of 7 and operation cycle time 72 h. In the subsequent experiment all optimum conditions were combined in a single experiment where 73.91% of decolorization efficiency was achieved. For the evaluation of metabolites formed after decolorization/degradation the aliquots containing bacteria were homogenized, filtered and then subjected to extraction. The extracted metabolites were then subjected to the silica gel column isolation. UV–Vis, FTIR, and NMR techniques were used to elucidate structures of the metabolites. Out of the collected metabolites only P-xylene was identified, which has been formed by cleavage of azo linkage by azo reductase enzyme of bacteria following the deamination and methylation of nitro substituted benzene ring.

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Water pollution due to textile dyes is a serious threat to every life form. Bacteria can degrade and detoxify toxic dyes present in textile effluents and wastewater. The present study aimed to evaluate the degradation potential of eleven bacterial strains for azo dye methyl red. The optimum degradation efficiency was obtained using P. aeruginosa. It was found from initial screening results that P. aeruginosa is the most potent strain with 81.49% degradation activity and hence it was subsequently used in other degradation experiments. To optimize the degradation conditions, a number of experiments were conducted where only one variable was varied at a time and where maximum degradation was observed at 20 ppm dye concentration, 1666.67 mg/L glucose concentration, 666.66 mg/L sodium chloride concentration, pH 9, temperature 40 °C, 1000 mg/L urea concentration, 3 days incubation period, and 66.66 mg/L hydroquinone (redox mediator). The interactive effect of pH, incubation time, temperature, and dye concentration in a second-order quadratic optimization of process conditions was found to further enhance the biodegradation efficiency of P. aeruginosa by 88.37%. The metabolites of the aliquot mixture of the optimized conditions were analyzed using Fourier transform infrared (FTIR), GC-MS, proton, and carbon 13 Nuclear Magnetic Resonance (NMR) spectroscopic techniques. FTIR results confirmed the reduction of the azo bond of methyl red. The Gas Chromatography–Mass Spectrometry (GC-MS) results revealed that the degraded dye contains benzoic acid and o-xylene as the predominant constituents. Even benzoic acid was isolated from the silica gel column and identified by 1H and 13C NMR spectroscopy. These results indicated that P. aeruginosa can be utilized as an efficient strain for the detoxification and remediation of industrial wastewater containing methyl red and other azo dyes.

Puerol A (1) from Amorpha fruticosa showed highly potent inhibition against both monophenolase (IC50 = 2.2 μM) and diphenolase (IC50 = 3.8 μM) of tyrosinase. We tried to obtain a full story of enzyme inhibitory behavior for inhibitor 1 because the butenolide skeleton has never been reported as a tyrosinase inhibitor. Puerol A was proved as a reversible, competitive, simple slow-binding inhibitor, according to the respective parameters; k3 = 0.0279 μM−1 min−1 and k4 = 0.003 min−1. A longer lag-phase and a reduced static-state activity of the enzyme explained that puerol A had a tight formation of the complex with Emet. Dose-dependent inhibition was also confirmed by high-performance liquid chromatography (HPLC) analysis using N-acetyl-l-tyrosine as a substrate, which was completely inhibited at 20 μM. A high binding affinity of 1 to tyrosinase was confirmed by fluorescence quenching analysis. Moreover, puerol A decreased melanin content in the B16 melanoma cell dose-dependently with an IC50 of 11.4 μM.

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