Isolation and characterization of a Pseudomonas strain, isolate TW1008, which aerobically metabolizes P-((2-hydroxy-1-naphthyl)azo)-benzenesulfonic acid

The compound 4{dollar}spprime{dollar}-((2-hydroxy-1-naphthyl)azo) benzenesulfonic acid (Acid Orange 7; C.I. 15510) is an anionic monoazo dye and a member of the largest category of synthetic commercial colorants, i.e., azo dyes. Acid Orange 7 (AO7) is a sulfonated dye which is representative of azo dyes recalcitrant to biodegradation. Numerous members of this group of non-heterocyclic aromatic nitrogen-containing compounds pose potential health hazards, i.e., due to toxicity or carcinogenicity of some dyes, but more significantly, due to by-products or precursors. The efficacious treatment modality for azo dyes is aerobic, since under anaerobic conditions these dyes act as artificial electron acceptors, producing aromatic amines; many of these products are known carcinogens. Azo dyes are environmentally significant, since approximately 60,000 tons of azo dyes are released annually into the environment from dye manufacturing and application industries.; A bacterial strain, TW1008, speciated as Pseudomonas putida, Biotype B, was isolated from a microbial consortium that had been maintained under aerobic conditions in a solution containing minimal salts, glucose and L-glutamic acid. Subsequently, TW1008 was determined to utilize purified AO7 (99.7% purity) as a sole source of carbon, nitrogen and energy, under aerobic conditions. Analysis of the spent medium by HPLC showed AO7 to be degraded {dollar}>{dollar}95%. During the early phase of metabolism, there was a concomitant appearance and increase in sulfanilic acid (an initial degradation product) concentration with AO7 disappearance in solution. Time-course studies showed that sulfanilic acid was metabolized by TW1008, during later phases of microbial activity. This finding was noteworthy, since sulfanilic acid has consistently been reported by numerous researchers to exert an inhibitory influence on the catabolic activities of other bacterial species.; The most significant finding in this work was the isolation of an aerobic organism that has the metabolic capabilities to catalyze the three key reactions required for biodegradation and detoxification of azo dyes and metabolites; These are: (1) Cleavage of the azo bond under aerobic conditions; (2) Metabolism of the sulfonated intermediates of azo dye biodegradation; (3) Utilization of the azo dyes and metabolic intermediates for sole sources of carbon and nitrogen for growth, thereby detoxifying these compounds.