Reduction of azo dyes by redox mediators originating in the naphthalenesulfonic acid degradation pathway of Sphingomonas sp. strain BN6

Two biological approaches for decolorization of azo sulfonated dyes have been compared: reductive decolorization with the ascomycete yeast Issatchenkia occidentalis and enzymatic oxidative decolorization with Trametes villosa laccase alone or in the presence of the mediator 1-hydroxybenzotriazole. The redox potential difference between the biological cofactor involved in the reductive activity of growing cells and the azo dye is a reliable indication for the decolorization ability of the biocatalyst. A linear relationship exists between the redox potential of the azo dyes and the decolorization efficiency of enzyme, enzyme/mediator, and yeast. The less positive the anodic peak of the dye, the more easily it is degraded oxidatevely with laccase. The more positive the cathodic peak of the dye, the more rapidly the dye molecule is reduced with yeast.

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“…The substituents next to the azo bond affect the rate of azo dyes reduction (30). The process is also facilitated by redox mediators (31).…”

Section: Resultsmentioning

confidence: 99%

Predicting Dye Biodegradation from Redox Potentials

et al. 2004

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“…Nevertheless, Tratnyek and Macalady (1989) and Curtis and Reinhard (1994) were probably the first researchers to focus their research on evidencing the input of RM on the reduction of nitroaromatics and polyhalogenated pollutants, respectively. From then on, and certainly after the publication of other thorough papers on basic aspects of the role of RM (Keck et al, 1997;Kudlich et al, 1997) and the boosting attention to microbial fuel cells (Bullen et al, 2006;Logan et al, 2006) the topic became increasingly popular, both in basic and in applied research. The application of RM for wastewater treatment and aquifer bioremediation has deserved considerable attention during the last years.…”

Section: Introductionmentioning

confidence: 99%

Impact and application of electron shuttles on the redox (bio)transformation of contaminants: A review

Zee¹,

Cervantes²

2009

Biotechnology Advances

428

198

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During the last two decades, extensive research has explored the catalytic effects of different organic molecules with redox mediating properties on the anaerobic (bio)transformation of a wide variety of organic and inorganic compounds. The accumulated evidence points at a major role of electron shuttles in the redox conversion of several distinct contaminants, both by chemical and biological mechanisms. Many microorganisms are capable of reducing redox mediators linked to the anaerobic oxidation of organic and inorganic substrates. Electron shuttles can also be chemically reduced by electron donors commonly found in anaerobic environments (e.g. sulfide and ferrous iron). Reduced electron shuttles can transfer electrons to several distinct electron-withdrawing compounds, such as azo dyes, polyhalogenated compounds, nitroaromatics and oxidized metalloids, among others. Moreover, reduced molecules with redox properties can support the microbial reduction of electron acceptors, such as nitrate, arsenate and perchlorate. The aim of this review paper is to summarize the results of reductive (bio)transformation processes catalyzed by electron shuttles and to indicate which aspects should be further investigated to enhance the applicability of redox mediators on the (bio)transformation of contaminants.

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“…Therefore, the dosage of these compounds may represent an interesting option to increase the rates of electron transfer and subsequent reductive decolorization in bioreactors. Initially nonspecific enzymes reduce the mediators, which are subsequently chemically reoxidized by the reduction of the azo dyes (16). The reduction of the mediator in whole cells, which can occur either intracellularly (13) or extracellularly by a membrane-bound enzyme (17), will depend on many factors such as its size, polarity, standard redox potential (E 0 ′) and other physical-chemical characteristics (14).…”

Section: Introductionmentioning

confidence: 99%

Azo Dye Reduction by Mesophilic and Thermophilic Anaerobic Consortia

Santos

Madrid

Stams

et al. 2008

Biotechnol Progress

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The reduction of the azo dye model compounds Reactive Red 2 (RR2) and Reactive Orange 14 (RO14) by mesophilic (30 degrees C) and thermophilic (55 degrees C) anaerobic consortia was studied in batch assays. The contribution of fermentative and methanogenic microorganisms in both temperatures was evaluated in the presence of the fermentative substrate glucose and the methanogenic substrates acetate, H2/CO2, methanol, and formate. Additionally, the effect of the redox mediator riboflavin on electron shuttling was assessed. We concluded that the application of thermophilic anaerobic treatment is an interesting option for the reductive decolorization of azo dyes compared to mesophilic conditions. The use of high temperature may decrease or even take the place of the need for continuous redox mediator dosage in bioreactors, contrarily to the evident effect of those compounds on dye reduction under mesophilic conditions. Both fermenters and methanogens may play an important role during reductive decolorization of dyes, in which mediators are important not only for allowing the different microbes to participate more effectively in this complex reductive biochemistry but also for assisting in the competition for electrons between dyes and other organic and inorganic electron acceptors.

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Reduction of azo dyes by redox mediators originating in the naphthalenesulfonic acid degradation pathway of Sphingomonas sp. strain BN6

Cited by 177 publications

References 35 publications

Predicting Dye Biodegradation from Redox Potentials

Predicting Dye Biodegradation from Redox Potentials

Impact and application of electron shuttles on the redox (bio)transformation of contaminants: A review

Azo Dye Reduction by Mesophilic and Thermophilic Anaerobic Consortia

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