Azoreductase activity of dye-decolorizing bacteria isolated from the human gut microbiota

• Published in: Scientific reports Vol. 9; no. 1; p. 5508
• Main Authors: Zahran, Sara A., Ali-Tammam, Marwa, Hashem, Abdelgawad M., Aziz, Ramy K., Ali, Amal E.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 02-04-2019; Nature Publishing Group
• Subjects: 45; 45/77; 631/326/1320; 631/326/2522; Adult; Amaranth; Amaranth Dye - chemistry; Azo Compounds - chemistry; Azo dyes; Azoreductase; Bacillus cereus - enzymology; Bacillus cereus - isolation & purification; Bacteria - classification; Bacteria - enzymology; Bacteria - isolation & purification; Bacterial Proteins - metabolism; Biodegradation; Dyes; E coli; Enterococcus - enzymology; Enterococcus - isolation & purification; Enterococcus faecalis - enzymology; Enterococcus faecalis - isolation & purification; Enzymatic activity; Escherichia coli - enzymology; Escherichia coli - isolation & purification; Female; Food additives; Food dyes; Gastrointestinal Microbiome; Gene pool; Humanities and Social Sciences; Humans; Hydrogen-Ion Concentration; Intestinal microflora; Kinetics; Male; Microbiota; multidisciplinary; NADH; NADH, NADPH Oxidoreductases - metabolism; pH effects; Polymers; Primers; Science; Science (multidisciplinary); Young Adult
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-41894-8

The gut microbiota enriches the human gene pool and contributes to xenobiotic metabolism. Microbial azoreductases modulate the reduction of azo-bonds, activating produgs and azo polymer-coated dosage forms, or degrading food additives. Here, we aimed to screen the healthy human gut microbiota for food colorant-reducing activity and to characterize factors modulating it. Four representative isolates from screened fecal samples were identified as
E. coli
(AZO-Ec),
E. faecalis
(AZO-Ef),
E. avium
(AZO-Ev) and
B. cereus
(AZO-Bc). Both AZO-Ef and AZO-Ev decolorized amaranth aerobically and microaerophilically while AZO-Ec and AZO-Bc had higher aerobic reduction rates. The isolates varied in their activities against different dyes, and the azo-reduction activity mostly followed zero-order reaction kinetics, with a few exceptions. Additionally, the isolates had different pH dependence, e.g., AZO-Ec was not affected by pH variation while AZO-Bc exhibited variable degradation kinetics at different pH levels. Cell-free extracts showed NADH-dependent enzymatic activities 14–19 times higher than extracellular fractions. FMN did not affect the reducing activity of AZO-Ef cell-free extract, whereas AZO-Ec, AZO-Ev and AZO-Bc had significantly higher reduction rates in its presence (
P
 values
 = 
0.02, 0.0001 and 0.02, respectively). Using Degenerate primers allowed the amplification of azoreductase genes, whose sequences were 98–99% similar to genes encoding FMN-dependent-NADH azoreductases.