E. Razoflores et al., COMPLETE BIODEGRADATION OF THE AZO-DYE AZODISALICYLATE UNDER ANAEROBIC CONDITIONS, Environmental science & technology, 31(7), 1997, pp. 2098-2103
Azo dyes are a widespread class of poorly biodegradable industrial pol
lutants. In anaerobic environments, azo bonds are reductively cleaved
yielding carcinogenic aromatic amines, many of which are assumed to re
sist further metabolism by anaerobes. Here we report for the first tim
e that an azo dye compound is completely biodegradable in the absence
of oxygen. A pharmaceutical azo dye, azo-disalicylate, constructed fro
m two 5-aminosalicylic acid (5ASA) molecules was mineralized in an ada
pted methanogenic consortium to CH4 and NH3 with transient accumulatio
n of 5ASA as a degradation intermediate in both batch assays and conti
nuous bioreactors. The anaerobic metabolism of 5ASA was shown to provi
de the electrons required for the initial reductive cleavage of the az
o group. Our results suggest that it is possible to design azo dyes th
at are fully mineralized in the environment; thereby, avoiding accumul
ation of notorious toxic intermediates.