Reductive Cleavage Of Azo Bond Research Articles

Harnessing Chlorella vulgaris for the phycoremediation of azo dye: A comprehensive analysis of metabolic responses and antioxidant system

This study investigates the phycoremediation potential of microalgae Chlorella vulgaris in the degradation of Direct green 6 (DG6), a synthetic azo dye commonly used in the textile industry, which poses significant environmental and health risks due to its toxic and carcinogenic properties. Over 50 days of treatment, we analyzed the effects of varying concentrations of DG6 on the biodegradation capabilities of C. vulgaris with the characterization of growth and antioxidant parameters. The findings demonstrate that C. vulgaris reduced DG6 levels significantly (p < 0.05) at higher temperatures (40 °C) compared to other environmental ambient temperatures. Within the acidic range pH < 7 progressive removal efficiency was observed within 25 days in consistency with the enhanced growth indices of biomass concentration (Xm), productivity (Px), specific growth rate (μm), and doubling time (td) at the higher concentration of 60 mg L−1. Induction of both enzymatic and non-enzymatic antioxidant activities were quantified for superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), azoreductase, and laccase, as well as changes in the total ascorbate pool (AsA + DHA) and ferric reducing antioxidant power (FRAP). Furthermore, the underlying biodegradation mechanisms were elucidated by identifying the reductive cleavage of azo bonds by azoreductase and breakdown by peroxidases and laccase. These molecular by-products were identified using gas chromatography–mass spectrometry (GC–MS), which shed light on the metabolic pathways involved in DG6 biodegradation. This study underscores the effectiveness of C. vulgaris as a sustainable, low-cost solution for the bioremediation of azo-dye-polluted water. This study lays the groundwork for further exploration into the genetic and metabolic adaptations of algae under complex organic pollutant stress, with potential implications for ecophysiology, biotic interactions, and evolutionary biology.

Turning Waste into Useful Products by Photocatalysis with Nanocrystalline TiO2 Thin Films: Reductive Cleavage of Azo Bond in the Presence of Aqueous Formate.

UV-photoexcitation of TiO2 in contact with aqueous solutions of azo dyes does not imply only its photocatalytic degradation, but the reaction fate of the dye depends on the experimental conditions. In fact, we demonstrate that the presence of sodium formate is the switch from a degradative pathway of the dye to its transformation into useful products. Laser flash photolysis experiments show that charge separation is extremely long lived in nanostructured TiO2 thin films, making them suitable to drive both oxidation and reduction reactions. ESR spin trapping and photoluminescence experiments demonstrate that formate anions are very efficient in intercepting holes, thereby inhibiting OH radicals formation. Under these conditions, electrons promoted in the conduction band of TiO2 and protons deriving from the oxidation of formate on photogenerated holes lead to the reductive cleavage of N=N bonds with formation and accumulation of reduced intermediates. Negative ion ESI–MS findings provide clear support to point out this new mechanism. This study provides a facile solution for realizing together wastewater purification and photocatalytic conversion of a waste (discharged dye) into useful products (such as sulfanilic acid used again for synthesis of new azo dyes). Moreover, the use of TiO2 deposited on an FTO (Fluorine Tin Oxide) glass circumvents all the difficulties related to the use of slurries. The obtained photocatalyst is easy to handle and to recover and shows an excellent stability allowing complete recyclability.

Role of Azoreductases in Bacterial Decolorization of Azo Dyes

Azo dyes are largest class of synthetic dyes used in textile industries. The disposal of wastewater from textile industry may have serious environmental concern. Bacterial decolorization of azo dyes from textile wastewater is an environment friendly and cost effective treatment system. Various species of bacteria produces azoreductase enzyme which have shown great potential to decolorize the textile azo dyes via reductive cleavage of azo bond under anaerobic or aerobic conditions.

Decolorization of azo dye methyl red by suspended and co-immobilized bacterial cells with mediators anthraquinone-2,6-disulfonate and Fe3O4 nanoparticles

In this study, the decolorization and degradation of methyl red (MR) by suspended and immobilized cells of Aeromonas jandaei strain SCS5 under anaerobic and aerobic conditions have been investigated. The complete decolorization of MR at a concentration of 100 mg L−1 by A. jandaei strain SCS5 was obtained within 6 h for both anaerobic and aerobic suspended cultures, where the decolorization rate was faster in acidic conditions than basic conditions. The decolorization efficiency under 6 h increased with increasing cell mass of inoculation and decreased with increasing initial dye concentrations. Immobilized cells of A. jandaei strain SCS5 could decolorize MR, and the decolorization rate was significantly enhanced by cells immobilized with mediators such as anthraquinone-2,6-disulphonate and magnetic Fe3O4 nanoparticles compared to immobilized cells only. Moreover, the immobilized bacterial beads with mediators retained high decolorization activity up to more than 10 repeating cycles. UV–visible spectra (200–800 nm) and gas chromatography-mass spectrometry analysis demonstrated that MR was degraded by A. jandaei strain SCS5 through reductive cleavage of azo bond. MR degradation products showed less phytotoxicity against Triticum aestivum and Phaseolus mungo compared to untreated MR. This study has demonstrated that A. jandaei strain SCS5 could be a promising microbiological agent for the removal of azo dyes from the environment.

The biological in vitro effect and selectivity shown by a CoIIcomplex of 2-(2-hydroxyphenylazo)-indole-3′-acetic acid on three distinctly different cancer cells

Reductive cleavage of azo bond in a CoIIcomplex of HPIA decreased significantly implying less toxicity. On human colon carcinoma HCT116, ALL MOLT-4 &amp; MCF-7 breast cancer cells complex was more effective than HPIA but less toxic towards normal cells.

Linkage of iron elution and dissolved oxygen consumption with removal of organic pollutants by nanoscale zero-valent iron: Effects of pH on iron dissolution and formation of iron oxide/hydroxide layer.

The iron elution and dissolved oxygen (DO) consumption in organic pollutant removal by nanoscale zero-valent iron (nZVI) was examined in the range of solution pH from 3.0 to 9.0. Their behaviors were linked with the removal of organic pollutant through the dissolution of iron and the formation of iron oxide/hydroxide layer affected strongly by solution pH and DO. As an example of organic pollutants, azo-dye Orange II was chosen in this study. The chemical composition analyses before and after reaction confirmed the corrosion of nZVI into ions, the formation of iron oxide/hydroxide layer on nZVI surface and the adsorption of the pollutant and its intermediates. The complete decolorization of Orange II with nZVI was accomplished very quickly. On the other hand, the total organic carbon (TOC) removal was considerably slow and the maximum TOC removal was around 40% obtained at pH 9.0. The reductive cleavage of azo-bond by emitted electrons more readily took place as compared with the cleavage of aromatic rings of Orange II leading to the degradation to smaller molecules and subsequently the mineralization. A reaction kinetic model based on the Langmuir-Hinshelwood/Eley-Rideal approach was developed to elucidate mechanisms for organic pollutant removal controlled by the formation of iron oxide/hydroxide layer, the progress of which could be characterized by considering the dynamic concentration changes in Fe(2+) and DO. The dynamic profiles of Orange II removal linked with Fe(2+) and DO could be reasonably simulated in the range of pH from 3.0 to 9.0.

Yeast extract promotes decolorization of azo dyes by stimulating azoreductase activity in Shewanella sp. strain IFN4

Biological treatment of azo dyes commonly requires a combined anaerobic–aerobic process in which initial decolorization is achieved by reductive cleavage of azo bonds on the parent molecule. The present study was conducted to examine the relative importance of co-substrates for driving reductive decolorization of azo dyes by Shewanella sp. strain IFN4 using whole cells and enzyme assays. Results showed that the dye decolorization by strain IFN4 was faster in medium containing 1gL−1 yeast extract (YE) as compared to nine other co-substrates. Moreover, only YE stimulated azoreductase activity (increased from 1.32 to 4.19U/mg protein). Increasing the level of YE up to 8gL−1 resulted into 81% decolorization of the dye in 1h along with an increase in azoreductase activity up to 6.16U/mg protein. Among the components of YE, only riboflavin stimulated the decolorization process as well as enzyme activity. Moreover, strain IFN4 demonstrated flavin reductase activity, and a significant correlation (r2=0.98) between flavin reduction and dye reduction by this strain emphasized the involvement of flavin compounds in the decolorization process. The results of this study show that YE serves both as a source of reducing equivalents and an electron shuttle for catalyzing dye reduction.

Synthesis and characterization of 5-amino-2-((3-hydroxy-4-((3-hydroxyphenyl) phenyl) diazenyl) phenol and its Cu(II) complex – a strategy toward developing azo complexes for reduction of cytotoxicity

A major drawback of azo compounds is their associated toxicity, often carcinogenic, which is related to the reduction of the azo bond. This study intends to re-investigate this behavior by studying 5-amino-2-((3-hydroxy-4-((3-hydroxyphenyl) phenyl) diazenyl) phenol (AHPD), a compound containing two azo bonds. Interaction of AHPD and its dimeric Cu(II) complex with bacterial strains Escherichia coli and Staphylococcus aureus revealed the complex was less toxic. Reductive cleavage of the azo bond in AHPD and the complex followed using cytochrome c reductase (a model azo-reductase) as well as azo-reductase enzymes obtained from bacterial cell extracts. Degradation of the azo bond was less in the complex allowing us to correlate the observed cytotoxicity. Cyclic voltammetry on AHPD and the complex support observations of enzyme assay experiments. These were particularly useful in realizing the formation of amines as an outcome of the reductive cleavage of azo bonds in AHPD that could not be identified through...

Biodegradation and Decolorization of Acid Red by Acinetobacter radioresistens

Acid red decolorizing bacteria was isolated and identified as Acinetobacter radioresistens.The effect of operation parameters such as medium composition, pH, temperature, dye concentration on the decolorization of acid red was studied and the products of degradation were analyzed and confirmed using LC–MS analysis. The reductive cleavage of azo bond was catalyzed by azoreductase, the key enzyme for the azo dye degradation. The catalytic reduction of acid red 37 by purified azoreductase in the presence of NADH as electron donor was studied and the products of degradation were determined as 1-{3-amino-5-[(aminoxy)sulfonyl]phenyl}ethanol and 7,8-diamino-3[(aminoxy)sulfonyl]naphthalene-1-ol.

Electrochemical removal of CI Acid orange 10 from aqueous solutions

The removal of CI Acid orange 10 from aqueous solutions was studied by electrocoagulation and electrooxidation techniques. For electrocoagulation, metallic iron was used as electrodes whereas graphite and IrO 2/TaO 2/RuO 2 coated titanium were used in the case of electrooxidation. During electro-coagulation, the CI Acid orange 10 molecule was split into aniline and 1-amino-2-naphthol-6,8-disulfonic acid due to reductive cleavage of azo bond. The latter was found to co-precipitate with iron oxy-hydroxide whereas aniline remained in aqueous phase. The zeta-potential measurements and FT-IR spectroscopic studies have revealed the chemical interaction between 1-amino-2-naphthol-6,8-disulfonic acid and iron oxy-hydroxide which formed as a result of anodic dissolution. De-colorization and degradation of the dye was followed using UV–Vis spectroscopy, GC–MS and TOC measurements. The CI Acid orange 10 was completely oxidized and removed with graphite electrodes. However the oxidation was only partial with IrO 2/TaO 2/RuO 2 coated titanium electrodes. The effect of initial pH and current density on the removal of CI Acid orange 10 was discussed.

Decolourization of azo dyes using magnesium–palladium system

Magnesium–palladium system was found to efficiently decolourize reactive black 5, sunset yellow FCF and tartrazine dyes. There is complete loss of visible range absorption peaks and extent of colour removal exceeded 95% within 24 h of reaction. There is appearance of new peak(s) in the UV region and/or gradual and significant shift of the λ max in the UV range during 1–24 h of reaction of dyes with Mg/Pd system. LC–MS analyses following the reaction of dyes with magnesium palladium system suggest reductive cleavage of azo bonds and formation of amines as the end products. Kinetic analyses of dye decolourization indicate that the reaction follows first order kinetics. Agreement between the experimental and predicted Michaelis–Menten plots for the decolourization of reactive black 5, sunset yellow FCF and tartrazine dyes by Mg 0/Pd 4+ system, suggests the correctness of Michaelis–Menten model for the prediction of dye decolourization rates by Mg 0/Pd 4+ system. Our investigations reveal that Mg 0/K 2PdCl 6 system is more effective in decolourizing dyes as compared to Mg 0/Pd 0–alumina or Mg 0 alone. Results obtained from reuse experiments suggest that Pd 0 pellets have the potential for recycling which will make the treatment process cost effective. Mg 0/Pd 4+ system was found to be efficient in decolourizing mixture of drimarene, remazol and procion dyes as well as raw effluent generated by textile dye manufacturing company.

Isolation and Characterization of Aeromonas sp. B-5 Capable of Decolorizing Various Dyes.

Aeromonas sp. B-5, which has the ability to decolorize azo dyes, was isolated from soil. Aeromonas sp. B-5 completely decolorized 100 mg/ l of Bordeaux S by reductive cleavage of azo bonds under static conditions in 24 h. Though the decolorization of Bordeaux S by Aeromonas sp. B-5 was suppressed under shaking, rapid decolorization was observed when the culture was changed to static conditions after cultivation with shaking. The indigoid dye, Acid blue 74, was decolorized by Aeromonas sp. B-5 under shaking conditions, in contrast to the decolorization of azo dyes.

Isolation and characterization of Aeromonas sp. B-5 capable of decolorizing various dyes

Aeromonas sp. B-5, which has the ability to decolorize azo dyes, was isolated from soil. Aeromonas sp. B-5 completely decolorized 100 mg/ l of Bordeaux S by reductive cleavage of azo bonds under static conditions in 24 h. Though the decolorization of Bordeaux S by Aeromonas sp. B-5 was suppressed under shaking, rapid decolorization was observed when the culture was changed to static conditions after cultivation with shaking. The indigoid dye, Acid blue 74, was decolorized by Aeromonas sp. B-5 under shaking conditions, in contrast to the decolorization of azo dyes.

Decolorization of Reactive Dyes and Dyeing Wastewater by Microorganisms under Anaerobic Conditions

The decolorizations of four reactive dyes with azo or anthraquinone group, printing wastewater and winch wastewater were investigated using microorganisms under anaerobic conditions. Reactive dyes with azo group were effectively decolorized. The mechanism of decolorization was suggested to be a reductive cleavage of azo bond. Decolorization rate increased in the presence of organic nutrients such as desizing wastewater. Decolorizations of printing and winch wastewaters were easily achieved as good as for azo dyes. For an artificial wastewater made from 70% of the solution of four reactive dyes and 30% of desizing wastewater, 85% decolorization and 65% COD removal were attained using anaerobic-aerobic continuous treatment.