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Evidence for Significantly Enhancing Reduction of Azo Dyes in Escherichia coli by Expressed Cytoplasmic Azoreductase (AzoA) of Enterococcus faecalis

[ Vol. 17 , Issue. 5 ]


Jinhui Feng, Thomas M. Heinze, Haiyan Xu, Carl E. Cerniglia and Huizhong Chen   Pages 578 - 584 ( 7 )


Although cytoplasmic azoreductases have been purified and characterized from various bacteria, little evidence demonstrating that these azoreductases are directly involved in azo dye reduction in vivo is known. In order to evaluate the contribution of the enzyme to azo dye reduction in vivo, experiments were conducted to determine the effect of a recombinant cytoplasmic azoreductase (AzoA) from Enterococcus faecalis expressed in Escherichia coli on the rate of metabolism of Methyl Red, Ponceau BS and Orange II. The intact cells that contained IPTG induced AzoA had a higher rate of dye reduction with increases of 2 (Methyl Red), 4 (Ponceau BS) and 2.6 (Orange II)-fold compared to noninduced cells, respectively. Metabolites of Methyl Red isolated from induced cultures were identified as N,N-dimethyl-pphenylenediamine and 2-aminobenzoic acid through liquid chromatography electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) analyses. In conclusion, our data demonstrate that AzoA from Ent. faecalis is capable of increasing the reduction of azo dyes in intact E. coli cells and that cytoplasmic azoreductase is involved in bacterial dye degradation in vivo.


Enterococcus faecalis, azoreductase, Azo dye, NADH, decolorization


Division of Microbiology, National Center for Toxicological Research, U.S. FDA, 3900 NCTR Rd., Jefferson, AR 72079-9502, USA.

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