Mechanisms of Azo Reduction by<i>Streptococcus faecalis</i>II. The Role of Soluble Flavins

Gingell, Ralph; Walker, Ronald W.

doi:10.3109/00498257109033172

Cited by 147 publications

(58 citation statements)

References 17 publications

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“…This activity, however, cannot be attributed to the catalase-peroxidase previously isolated from this organism, which did not attack any of the tested dyes (13). An intracellular azoreductase (EC 1.7.1.6 [azobenzene reductase]) is responsible for the decolorization activity, as previously shown for other azo-dye-degrading microorganisms (11,31,36). Two bands showing azoreductase activity were found after separation of the cell lysate from Bacillus strain SF in gels combined with activity staining.…”

Section: Discussionmentioning

confidence: 59%

“…In contrast, under anaerobic conditions, the decolorization of many azo dyes via reduction of the azo bond has been shown for anaerobic (e.g., Bacteroides sp., Eubacterium sp., and Clostridium sp.) as well as facultative anaerobic (e.g., Proteus vulgaris and Streptococcus faecalis) bacteria (5,11,30,36). The main interest in this field has been focused on bacteria from the human intestine that are involved in the metabolism of azo dyes ingested as food additives (9).…”

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confidence: 99%

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A New Alkali-Thermostable Azoreductase from Bacillus sp. Strain SF

Maier

Kandelbauer

Erlacher

et al. 2004

Appl Environ Microbiol

217

100

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A screening for dye-decolorizing alkali-thermophilic microorganisms resulted in a Bacillus sp. strain isolated out of the wastewater drain of a textile finishing company. An NADH-dependent azoreductase of this strain, Bacillus sp. strain SF, was found to be responsible for the decolorization of azo dyes. This enzyme was purified by a combination of ammonium sulfate precipitation and anion-exchange and affinity chromatography and had a molecular mass of 61.6 kDa and an isoelectric point at pH 5.3. The pH optimum of the azoreductase depended on the substrate and was within the range of pHs 8 to 9, while the temperature maximum was reached at 80°C. Decolorization only took place in the absence of oxygen and was enhanced by FAD, which was not consumed during the reaction. A 26% similarity of this azoreductase to chaperonin Cpn60 from a Bacillus sp. was found by peptide mass mapping experiments. Substrate specificities of the azoreductase were studied by using synthesized model substrates based on di-sodium-(R)-benzyl-azo-2,7-dihydroxy-3,6-disulfonyl-naphthaline. Those dyes with NO 2 substituents, especially in the ortho position, were degraded fastest, while analogues with a methyl substitution showed the lowest degradation rates.In the last few years, environmental legislation, e.g., about the appearance of color in discharges, combined with the increasing cost of water for the industrial sector, has made the treatment and reuse of dyeing effluents increasingly attractive to the industry. The common method for the treatment of wastewater in the textile finishing industry is physicochemical flocculation in combination with biological treatment (17). The conventional treatment of colored effluents produces a lot of sludge, but does not remove all dyes, thus preventing recycling of the treated wastewater. In activated sludge treatments, dyeing effluents, e.g., reactive azo dyes and naphthaline-sulfonic acids as well as aromatic amino derivatives, represent an extensive nonbiodegradable class of compounds (18) and can even inhibit activated sludge organisms. Thus, the development of more effective biological systems for the treatment of these types of wastewater has resulted in considerable interest by the industry.Wood-rotting fungi (e.g., Phanerochaete chrysosporium, Trametes sp., and Aspergillus sp.) have been found to effectively degrade a variety of azo dyes under aerobic conditions (16). Dye-degrading fungi have been used frequently in bioreactors for the decolorization and degradation of azo dyes (37). While fungal treatment of effluents is usually very time-consuming (3), immobilized enzymes could have potential for dye decolorization and recycling of effluents (1) without the need for the addition of growth substrates. The enzymes involved in the degradation of azo dyes are mainly peroxidases (12) and laccases (1). However, a significant cost reduction for these enzymes would be required in order to make this process economically more attractive. Aerobic bacteria have been described to oxidatively decolorize m...

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Section: Discussionmentioning

confidence: 59%

mentioning

confidence: 99%

A New Alkali-Thermostable Azoreductase from Bacillus sp. Strain SF

Maier

Kandelbauer

Erlacher

et al. 2004

Appl Environ Microbiol

217

100

View full text Add to dashboard Cite

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“…A description of a nonspecific azo reductase system involved in azo dye reduction has been provided for selected bacterial species, and it has been shown that the MICROBIAL POPULATIONS TREATING DYE EFFLUENT 3231 relevant gene is relatively conserved in various anaerobic and facultative bacteria (24,46). Redox mediator compounds, such as flavins, have been shown to enhance degradation of azo dyes by acting as electron shuttles that facilitate reduction of the azo dye (13). In this research it was also hypothesized that coenzyme reducing equivalents involved in normal electron transport through oxidation of organic substrates may act as electron donors for reduction of azo dyes.…”

Section: Discussionmentioning

confidence: 99%

Microbial Populations Associated with Treatment of an Industrial Dye Effluent in an Anaerobic Baffled Reactor

Plumb

Bell

Stuckey

2001

Appl Environ Microbiol

112

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Fluorescent in situ hybridization (FISH) using 16S and 23S rRNA-targeted probes together with construction of an archaeal 16S ribosomal DNA (rDNA) clone library was used to characterize the microbial populations of an anaerobic baffled reactor successfully treating industrial dye waste. Wastewater produced during the manufacture of food dyes containing several different azo and other dye compounds was decolorized and degraded under sulfidogenic and methanogenic conditions. Use of molecular methods to describe microbial populations showed that a diverse group of Bacteria and Archaea was involved in this treatment process. FISH enumeration showed that members of the gamma subclass of the class Proteobacteria and bacteria in the Cytophaga-Flexibacter-Bacteroides phylum, together with sulfate-reducing bacteria, were prominent members of a mixed bacterial population. A combination of FISH probing and analysis of 98 archaeal 16S rDNA clone inserts revealed that together with the bacterial population, a methanogenic population dominated by Methanosaeta species and containing species of Methanobacterium and Methanospirillum and a relatively unstudied methanogen, Methanomethylovorans hollandica, contributed to successful anaerobic treatment of the industrial waste. We suggest that sulfate reducers, or more accurately sulfidogenic bacteria, together with M. hollandica contribute considerably to the treatment process through metabolism of dye-associated sulfonate groups and subsequent conversion of sulfur compounds to carbon dioxide and methane.

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“…A physiological role for azo reduction, as an electron sink during anaerobic growth, has been suggested for Ent. faecalis [47]. The ability to dispose of excess reducing power in this way would be energetically favourable to fermentative bacteria growing in the large gut.…”

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confidence: 99%

Ecological and physiological studies on large intestinal bacteria in relation to production of hydrolytic and reductive enzymes involved in formation of genotoxic metabolites

McBain

Macfarlane²

1998

Journal of Medical Microbiology

160

104

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Several hydrolytic and reductive bacterial enzymes (P-glucuronidase, GN; /3-glucosidase, GS; arylsulphatase, AS; azoreductase, AR; nitroreductase, NR) involved in production of mutagenic or genotoxic metabolites were measured in human colonic contents. Cellassociated AS and extracellular GS were approximately twice as high in the distal colon compared with the proximal bowel, while AR changed little throughout the gut. Measurements of these enzymes in faeces from seven healthy donors confirmed that the majority were cell-associated, and demonstrated high levels of inter-individual variability. NR decreased four-fold between the proximal and distal colon while extracellular GN was reduced by 50%. Most probable number (MPN) analysis on faeces obtained from six healthy donors showed that counts of intestinal bacteria producing GS and AR were c. 10" and 10l1/g, respectively, in all samples tested. Numbers of GN-and AS-forming organisms were between two and three orders of magnitude lower. Interindividual carriage rates of bacterial populations synthesising NR were highly variable. Screening of 20 pure cultures of intestinal bacteria, belonging to six different genera, showed that Bacteroides ovatus, in particular, synthesised large amounts of GS, whereas B. fragilis, B. vulgatus and Bijidobacterium pseudolongum formed the highest cellassociated levels of GN. In general, bifidobacteria and Lactobacillus acidophilus did not produce significant amounts of AR. All five clostridia studied (Clostridium bifementans, C. septicum, C. perfringens, C. sporogenes and C. butyricum) produced NR and AR, as did the bacteroides (B. fragilis, B. ovatus and B. vulgatus). Escherichia coli and C.perfringens formed large amounts of NR. Levels of AS production were invariably low and few of the organisms screened synthesised this enzyme. In-vitro studies investigating the effect of intestinal transit time on enzyme production, in a three-stage (Vl-V3) continuous culture model of the colon operated at system retention times (R) of either 31.1 or 68.4 h, showed that specific activities of GS were up to four-fold higher (V3) at R = 31.1 h. Bacteriological analysis demonstrated that representative populations of colonic micro-organisms were maintained in the fermentation system, and indicated that changes in GS activity were not related to numbers of the predominant anaerobic or facultative anaerobic species within the model, but were explainable on the basis of substrate-induced modulation of bacterial metabolism.

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Mechanisms of Azo Reduction byStreptococcus faecalisII. The Role of Soluble Flavins

Cited by 147 publications

References 17 publications

A New Alkali-Thermostable Azoreductase from Bacillus sp. Strain SF

A New Alkali-Thermostable Azoreductase from Bacillus sp. Strain SF

Microbial Populations Associated with Treatment of an Industrial Dye Effluent in an Anaerobic Baffled Reactor

Ecological and physiological studies on large intestinal bacteria in relation to production of hydrolytic and reductive enzymes involved in formation of genotoxic metabolites

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