Recent Advances in Azo Dye Degrading Enzyme Research

Chen, Huizhong

doi:10.2174/138920306776359786

Cited by 218 publications

(132 citation statements)

References 105 publications

(129 reference statements)

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“…In this study, azo dyes were oxidized without cleavage of the azo bond via free radical highly non-specific mechanism, forming phenolic type compounds. Toxic aromatic amines are not produced in this mechanism (Chen, 2006). Free radicals generated by a biotransformation process participate in coupling reactions with intact dye and/or intermediate molecules.…”

Section: Biodegradation Via Oxidative Processesmentioning

confidence: 99%

Bacterial diversity and composition in major fresh produce growing soils affected by physiochemical properties and geographic locations

Ibekwe

Yang

et al. 2016

Science of The Total Environment

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Azo dyes and their intermediate degradation products are common contaminants of soil and groundwater in developing countries where textile and leather dye products are produced. The toxicity of azo dyes is primarily associated with their molecular structure, substitution groups and reactivity. To avoid contamination of natural resources and to minimize risk to human health, this wastewater requires treatment in an environmentally safe manner. This manuscript critically reviews biological treatment systems and the role of bacterial reductive and oxidative enzymes/processes in the bioremediation of dye-polluted wastewaters. Many studies have shown that a variety of culturable bacteria have efficient enzymatic systems that can carry out complete mineralization of dye chemicals and their metabolites (aromatic compounds) over a wide range of environmental conditions. Complete mineralization of azo dyes generally involves a two-step process requiring initial anaerobic treatment for decolorization, followed by an oxidative process that results in degradation of the toxic intermediates that are formed during the first step. Molecular studies have revealed that the first reductive process can be carried out by two classes of enzymes involving flavin-dependent and flavin-free azoreductases under anaerobic or low oxygen conditions. The second step that is carried out by oxidative enzymes that primarily involves broad specificity peroxidases, laccases and tyrosinases. This review focuses, in particular, on the characterization of these enzymes with respect to their enzyme kinetics and the environmental conditions that are necessary for bioreactor systems to treat azo dyes contained in wastewater.

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Section: Biodegradation Via Oxidative Processesmentioning

confidence: 99%

Bacterial diversity and composition in major fresh produce growing soils affected by physiochemical properties and geographic locations

Ibekwe

Yang

et al. 2016

Science of The Total Environment

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“…Azo dyes are a major group of colorants used in textiles, plastics, pharmaceuticals, cosmetics and food products (Chen, 2006;Stolz, 2001). Many synthetic azo dyes can be converted to potentially carcinogenic aromatic amines after reduction (Platzek et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Functional role of Trp-105 of Enterococcus faecalis azoreductase (AzoA) as resolved by structural and mutational analysis

Chen

Kweon

et al. 2008

Microbiology

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Enterococcus faecalis azoreductase (AzoA) is a very active enzyme with a broad spectrum of substrate specificity and is capable of degrading various azo dyes. The enzyme has an absolute requirement for reduced FMN, which delivers a total of four electrons from NADH to the substrate, resulting in the cleavage of the nitrogen double bond. In this study, we report the identification of amino acid residues critical for FMN binding in AzoA. FMN is stabilized by 22 amino acid residues, eight of which, Trp-105, Asn-106, Leu-107, Gly-150, Gly-151, Tyr-153, Asn-121 and Tyr-129, are involved in binding the FMN isoalloxazine ring. In silico analysis of the amino acid residues revealed that the Trp residue at position 105 of AzoA is the most likely significant contributor to the binding of FMN to the enzyme and is involved in FMN stabilization and destabilization. Site-directed mutagenesis analysis of Trp-105 was performed to determine the role of this amino acid residue in FMN binding and azo dye reductive activity. The mutant proteins were overexpressed in Escherichia coli and purified by anion-exchange and size-exclusion chromatography. The replacement of Trp-105 by the small side-chain amino acids Ala and Gly caused complete loss of both affinity for FMN and enzyme activity. Substitution of Tyr for Trp-105 did not significantly decrease the V max of the enzyme (22 % reduction). Substitutions with three bulky side-chain amino acids, Gln, Phe and His, produced enzymes with lower V max values (decreases of 68.2, 30.6 and 8.2-fold, respectively). However, these mutated enzymes maintained K m values similar to the wild-type enzyme. This study provides an insight into the catalytic properties of AzoA in FMN stabilization and enzyme activity.

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“…Azo dyes are common synthetic colourants, which are used in many industries, spanning foods and beverages to textiles and paper products (Chen, 2006;Chung & Cerniglia, 1992). Azo dyes possess a namesake azo bond (-N5N-), which makes them capable of being reduced to their component aromatic amines by the azoreductase enzyme (Stolz, 2001).…”

Section: Introductionmentioning

confidence: 99%

“…However, in many cases, these aromatic amines have been found to be carcinogenic in nature (Rafii & Coleman, 1999). In addition to being a threat to human health, azo dyes are also frequently found as environmental pollutants, a result of industrial processing applications (Chen, 2006;Chung & Cerniglia, 1992;Stolz, 2001). …”

Section: Introductionmentioning

confidence: 99%

Growth and physiology of Clostridium perfringens wild-type and ΔazoC knockout: an azo dye exposure study

Morrison

John

2016

Microbiology

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Clostridium perfringens, a strictly anaerobic micro-organism and inhabitant of the human intestine, has been shown to produce the azoreductase enzyme AzoC, an NAD(P)H-dependent flavin oxidoreductase. This enzyme reduces azo dyes to aromatic amines, which are carcinogenic in nature. A significant amount of work has been completed that focuses on the activity of this enzyme; however, few studies have been completed that focus on the physiology of azo dye reduction. Dye reduction studies coupled with C. perfringens growth studies in the presence of ten different azo dyes and in media of varying complexities were completed to compare the growth rates and dye-reducing activity of C. perfringens WT cells, a C. perfringens DazoC knockout, and Bifidobacterium infantis, a non-azoreductase-producing control bacterium. The presence of azo dyes significantly increased the generation time of C. perfringens in rich medium, an effect that was not seen in minimal medium. In addition, azo dye reduction studies with the DazoC knockout suggested the presence of additional functional azoreductases in this medically important bacterium. Overall, this study addresses a major gap in the literature by providing the first look, to our knowledge, at the complex physiology of C. perfringens upon azo dye exposure and the effect that both azo dyes and the azoreductase enzyme have on growth.

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Recent Advances in Azo Dye Degrading Enzyme Research

Cited by 218 publications

References 105 publications

Bacterial diversity and composition in major fresh produce growing soils affected by physiochemical properties and geographic locations

Bacterial diversity and composition in major fresh produce growing soils affected by physiochemical properties and geographic locations

Functional role of Trp-105 of Enterococcus faecalis azoreductase (AzoA) as resolved by structural and mutational analysis

Growth and physiology of Clostridium perfringens wild-type and ΔazoC knockout: an azo dye exposure study

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