Anaerobic reduction of a sulfonated azo dye, Congo Red, by sulfate-reducing bacteria

The capacity for anaerobic decolorization of a sulfonated azo dye, Congo Red, by a strain of a sulfate-reducing bacterium was evaluated. After optimizing the growth rate of the bacteria on a simple carbon source and terminal electron acceptor pair, lactate and sulfate, respectively, the effect of th...

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Bibliographic Details
Published in:	Applied biochemistry and biotechnology Vol. 97; no. 3; pp. 147 - 163
Main Authors:	Diniz, P.E, Lopes, A.T, Lino, A.R, Serralheiro, M.L
Format:	Journal Article
Language:	English
Published:	Heidelberg Springer 01-03-2002 Springer Nature B.V
Subjects:	Anions Azo Compounds - metabolism Azo dyes Bacteria Biochemistry - methods Biological and medical sciences Biological treatment of waters Biotechnology Biotechnology - methods Carbon Carbon sources Chromatography, High Pressure Liquid color Coloring Agents - metabolism Congo Red - metabolism Congo Red - pharmacology culture media decolorization Desulfovibrio - metabolism Dose-Response Relationship, Drug Dyes Electrons Environment and pollution Fundamental and applied biological sciences. Psychology high performance liquid chromatography Industrial applications and implications. Economical aspects Ions Lactic Acid - pharmacology Liquid chromatography Metabolites Microbiology Microorganisms Models, Chemical Studies Sulfate reduction sulfate-reducing bacteria Sulfates Sulfates - metabolism Sulfides Time Factors Anaerobiosis Pollutant Sulfate-reducing bacteria Discoloration Reduction Industrial waste water Azo dye Waste water purification Textile industry Biological purification Sulfonate
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Summary:	The capacity for anaerobic decolorization of a sulfonated azo dye, Congo Red, by a strain of a sulfate-reducing bacterium was evaluated. After optimizing the growth rate of the bacteria on a simple carbon source and terminal electron acceptor pair, lactate and sulfate, respectively, the effect of the dye concentration on their growth rate was analyzed. The decolorization rate was affected by the dye concentration in the growth medium. The azo-bond cleavage mechanism of reductive decolorization with the formation of benzidine was consistent with the results, as this metabolite was identified by high-performance liquid chromatography. Several fractions of the culture medium, including lysed cell extracts, were examined for the capacity to reduce the azo dye. This reduction capacity was found in the culture medium in which the cells had previously grown. The results showed that the mechanism of reductive decolorization of this sulfonated azo dye was extracellular and nonenzymatic, consistent with the production of sulfide anion by the microorganisms while growing on lactate and sulfate. The sulfide anions were the cause of the reduction leading to the disappearance of color in the medium. To increase the rate of decolorization, the presence of ferrous ion was also necessary together with the lactate and sulfate substrates.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0273-2289 1559-0291 0273-2289
DOI:	10.1385/ABAB:97:3:147