Metabolism of azo food dyes by bacterial members of the human gut microbiome.

Objectives: We set out to survey the capacities of bacterial isolates from the human gut microbiome to reduce common azo food dyes in vitro.

Methods: A total of 206 strains representative of 124 bacterial species and 6 phyla were screened in vitro using a simple azo dye decolorization assay. Strains which showed azoreductive activity were characterized by studies of azoreduction kinetics and bacterial growth.

Results: Several groups of gut bacteria, including ones not previously associated with azoreduction, reduced one or more of the four azo food dyes commonly used in Canada: Allura Red, Amaranth, Sunset Yellow, and Tartrazine. Strains within some species differed in their azoreductive capabilities. Some strains displayed evidence of effects on growth related to the presence of azo dyes and/or the products of their azoreduction.

Conclusion: The continued widespread use of food azo dyes requires re-evaluation in light of the potential for disturbance of the gut microbial ecosystem resulting from azoreduction and the possibility of consequences for human health.