Reduction of Azo Food Dyes in Cultures of<i>Proteus vulgaris</i>

Dubin, Paul L.; Wright, K. L.

doi:10.3109/00498257509056126

Cited by 143 publications

(63 citation statements)

References 22 publications

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“…The removal efficiency for color was approximately 20 % at the 2-h HRT location and increased continuously to 80 % as the HRT increased. The ORP decreased from -260 to -310 mV at the highest location (corresponding to the 8-h HRT), and the redox potential is in a good agreement with the standard redox potentials for different azo dyes, generally between -430 and -180 mV (Dubin and Wright 1975). The SCOD levels did not change much up to the 6-h HRT height, but a higher organic removal was observed at the 8-h HRT location.…”

Section: Removal Efficiency Along the Uasb Reactor Heightsupporting

confidence: 53%

Enhanced bioremoval of refractory compounds from dyeing wastewater using optimized sequential anaerobic/aerobic process

Bae

Han

Kim

et al. 2016

Int. J. Environ. Sci. Technol.

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The upflow anaerobic sludge blanket process followed by the biological aerated filter process was employed to improve the removal of color and recalcitrant compounds from real dyeing wastewater. The highest removal efficiency for color was observed in the anaerobic process, at 8-h hydraulic retention time, seeded with the sludge granule. In the subsequent aerobic process packed with the microbe-immobilized polyethylene glycol media, the removal efficiency for chemical oxygen demand increased significantly to 75 %, regardless of the empty bed contact time. The average influent non-biodegradable soluble chemical oxygen demand was 517 mg/L, and the average concentration in effluent from the anaerobic reactor was 363 mg/L, suggesting the removal of some recalcitrant matters together with the degradable ones. The average nonbiodegradable soluble chemical oxygen demand in effluent from the aerobic reactor was 87, 93, and 118 mg/L, with the removal efficiency of 76, 74, and 67 %, at 24-, 12-, and 8-h empty bed contact time, respectively. The combined anaerobic sludge blanket and aerobic cell-entrapped process was effective to remove the refractory compounds from real dyeing wastewater as well as in reducing organic loading to meet the effluent discharge limits. This integrated process is considered an effective and economical treatment technology for dyeing wastewater.

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Section: Removal Efficiency Along the Uasb Reactor Heightsupporting

confidence: 53%

Enhanced bioremoval of refractory compounds from dyeing wastewater using optimized sequential anaerobic/aerobic process

Bae

Han

Kim

et al. 2016

Int. J. Environ. Sci. Technol.

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“…Furthermore, a comparison of the redox potentials of 1,2-DHN (E 0 Ј ϭ 140 mV) (18) and amaranth (E 0 Ј ϭ ca. Ϫ250 mV) (15) suggested that 1,2-DHN was not responsible for the observed effects. These observations together suggested that 1,2-DHN formed during the degradation of 2NS was further converted (biologically or chemically) to products which are more active as redox mediators.…”

Section: Discussionmentioning

confidence: 99%

Identification of Quinoide Redox Mediators That Are Formed during the Degradation of Naphthalene-2-Sulfonate by Sphingomonas xenophaga BN6

Keck

Rau

Reemtsma

et al. 2002

Appl Environ Microbiol

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During aerobic degradation of naphthalene-2-sulfonate (2NS), Sphingomonas xenophaga strain BN6 produces redox mediators which significantly increase the ability of the strain to reduce azo dyes under anaerobic conditions. It was previously suggested that 1,2-dihydroxynaphthalene (1,2-DHN), which is an intermediate in the degradative pathway of 2NS, is the precursor of these redox mediators. In order to analyze the importance of the formation of 1,2-DHN, the dihydroxynaphthalene dioxygenase gene (nsaC) was disrupted by gene replacement. The resulting strain, strain AKE1, did not degrade 2NS to salicylate. After aerobic preincubation with 2NS, strain AKE1 exhibited much higher reduction capacities for azo dyes under anaerobic conditions than the wild-type strain exhibited. Several compounds were present in the culture supernatants which enhanced the ability of S. xenophaga BN6 to reduce azo dyes under anaerobic conditions. Two major redox mediators were purified from the culture supernatants, and they were identified by high-performance liquid chromatography-mass spectrometry and comparison with chemically synthesized standards as 4-amino-1,2-naphthoquinone and 4-ethanolamino-1,2-naphthoquinone.Wastewaters from textile industries are often highly colored due to residual dyestuff from the dyeing processes. It has been estimated that up to 60% of the total dyestuff used in the dyeing processes may be found in the wastewaters (3). Only small amounts of these dyes are removed by conventional aerobic biological wastewater treatment systems (37, 46). On the other hand, it is well known that azo dyes are reduced anaerobically by different microorganisms, which usually results in the generation of colorless aromatic amines (2,5,7,12,14,51,56). These amines are in most cases recalcitrant under anaerobic conditions (6). Therefore, it has been repeatedly suggested that two-stage anaerobic-aerobic treatment systems should be used to reduce the azo dyes anaerobically and to mineralize the amines formed in a subsequent aerobic stage (1,36,38,45,51,54). The first successful example of mineralization of a sulfonated azo dye by an anaerobic-aerobic treatment process involved a 6-aminonaphthalene-2-sulfonate-degrading mixed bacterial culture. This culture consisted of the naphthalenesulfonate-degrading strain Sphingomonas xenophaga BN6 in a mutualistic coculture with other bacterial strains (21,34,50). Recently, it was found that strain BN6 uses a new mechanism for conversion of azo dyes. During aerobic degradation of naphthalene-2-sulfonate (2NS), redox mediators are released, which mediate the reduction of azo dyes under anaerobic conditions (27). It was proposed that these redox mediators shuttle electrons from the cells to the azo dyes, which results in purely chemical, extremely nonspecific, extracellular reductive cleavage of the azo bond. Aerobic preincubation of strain BN6 with 2NS increased subsequent anaerobic reduction of the azo dyes almost 20-fold. It was suggested that 1,2-dihydroxynaphthalene (1,2-DHN), which is the ...

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“…imately vary between Ϫ180 mV and Ϫ430 mV (11,35). It is expected that for the functioning of a quinone as an effective mediator the proper redox potential is not sufficient, but that also the transport of the reduction equivalents from the cellular system to the azo compounds is important, because most relevant azo compounds are either too polar (e.g., polysulfonated azo dyes) and/or too large (e.g., polymeric azo compounds) to passively diffuse through the cell membranes.…”

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confidence: 99%

Oxygen-Insensitive Nitroreductases NfsA and NfsB of Escherichia coli Function under Anaerobic Conditions as Lawsone-Dependent Azo Reductases

Rau

2003

Appl Environ Microbiol

119

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Quinones can function as redox mediators in the unspecific anaerobic reduction of azo compounds by various bacterial species. These quinones are enzymatically reduced by the bacteria and the resulting hydroquinones then reduce in a purely chemical redox reaction the azo compounds outside of the cells. Recently, it has been demonstrated that the addition of lawsone (2-hydroxy-1,4-naphthoquinone) to anaerobically incubated cells of Escherichia coli resulted in a pronounced increase in the reduction rates of different sulfonated and polymeric azo compounds. In the present study it was attempted to identify the enzyme system(s) responsible for the reduction of lawsone by E. coli and thus for the lawsone-dependent anaerobic azo reductase activity. An NADH-dependent lawsone reductase activity was found in the cytosolic fraction of the cells. The enzyme was purified by column chromatography and the amino-terminal amino acid sequence of the protein was determined. The sequence obtained was identical to the sequence of an oxygen-insensitive nitroreductase (NfsB) described earlier from this organism. Subsequent biochemical tests with the purified lawsone reductase activity confirmed that the lawsone reductase activity detected was identical with NfsB. In addition it was proven that also a second oxygen-insensitive nitroreductase of E. coli (NfsA) is able to reduce lawsone and thus to function under adequate conditions as quinone-dependent azo reductase.Azo dyes are widely used as dyes for textiles, food, cosmetics, and various other purposes (51). They are usually very stable under aerobic conditions and therefore resist biodegradation in conventional aerobic sewage treatment systems. In contrast, under anaerobic conditions various bacterial strains are able to reduce azo dyes to amines and thus decolorize the dyes (10, 39, 43). These anaerobic reactions are usually extremely unspecific with regard to the organisms involved and the dyes converted. In these processes, low-molecular-weight redox mediators (e.g., quinones) are often involved which are enzymatically reduced by the bacteria. The reduced mediator compounds (e.g., hydroquinones) can then reduce the azo compounds outside of the cells in a purely chemically and therefore extremely unspecific redox reaction (17,23).It was recently shown that among different quinones tested, especially anthraquinone-2-sulfonate (AQS) and lawsone (2-hydroxy-1,4-naphthoquinone) considerably increased the anaerobic reduction rates of azo dyes by Sphingomonas xenophaga BN6, Escherichia coli, and various other bacterial strains from different bacterial groups. For S. xenophaga BN6, AQS was identified as the most effective redox mediator from all quinones investigated and it was suggested that the membrane bound NADH:ubiquinone oxidoreductase of the respiratory chain was responsible for this activity (23,35). In contrast to S. xenophaga BN6, cells of E. coli demonstrated much higher reduction rates with lawsone compared to AQS (35). These results suggested that the reduction of lawsone by...

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Reduction of Azo Food Dyes in Cultures ofProteus vulgaris

Cited by 143 publications

References 22 publications

Enhanced bioremoval of refractory compounds from dyeing wastewater using optimized sequential anaerobic/aerobic process

Enhanced bioremoval of refractory compounds from dyeing wastewater using optimized sequential anaerobic/aerobic process

Identification of Quinoide Redox Mediators That Are Formed during the Degradation of Naphthalene-2-Sulfonate by Sphingomonas xenophaga BN6

Oxygen-Insensitive Nitroreductases NfsA and NfsB of Escherichia coli Function under Anaerobic Conditions as Lawsone-Dependent Azo Reductases

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