Azo dyes such as red 40 are characterized by an R1-N=N-R2 structure and are widely used in the food industry, but their anaerobic degradation in the gut microbiota by azoreductases originate toxic or mutagenic aromatic amines, so their use has been restricted in many countries. The aim of this study was to submit the red dye 40 to degradation by enterobacteria and partially characterize the products of its anaerobic reduction. Two enterobacteria isolated from an infant together with the reference strains: Escherichia coli DH5α, Escherichia coli E2348/69, Citrobacter rodentium DBS13 and Enterobacter cloacae were used to inoculate samples of 30 ppm of red dye 40. The degradation percentage was estimated by UV/Vis spectroscopy and the products of anaerobic reduction were characterized by HPLC. Enterobacter sp. and E. coli isolates from the infant fecal sample yielded a degradation of 60% and 49% respectively. With respect of the reference strains, the degradation percentages were high up more than 70%. The degradation of red dye 40 by the different types of bacteria used in this research revealed a formation of compounds analogous to 1-naphthol and aromatic amines.