In vitro mutagenicity of Acid Violet 7 and its degradation products by Pseudomonas putida mt-2: Correlation with chemical structures

Acid Violet 7 (AV7), a very important commercial azo dye used in the textile, food, paper and cosmetic industries, was degraded by Pseudomonas putida mt-2 at a concentration up to 200 mg/l. HPLC analysis of the biodegradation media revealed the presence of either 4′-aminoacetanilide (4′-AA) or 5-acetamido-2-amino-1-hydroxy-3,6-naphthalene disulfonic acid (5-ANDS) deriving from AV7 azoreduction which attests the expression of an azoreductase by this bacterium. These amines were identified only in media of static incubation, which is consistent with their biotransformation under shaken incubation (aerobic conditions). Pure azo dye, pure azoreduction products and total lyophilized biodegradation extracts were assayed for their mutagenic properties using Ames test. Mutagenicity of AV7 even with or without the S9 metabolizing system increased significantly after static biodegradation and totally disappeared after shaken incubation. In addition, mutagenicity of pure azo reduction products of AV7 was assessed and compared with that of the parent unsubstituted amines. 4′-AA exhibited a strong mutagenicity which was imputed to the presence of the acetoxy (COCH3) substituent on the aromatic amine; however, the presence of sulphonic groups in 5-ANDS limited its mutagenicity.