Isolation and characterization of a pseudomonas strain that degrades 4-acetamidophenol and 4-aminophenol

Though many microorganisms that are capable of using phenol as sole source of carbon have been isolated and characterized, only a few organisms degrading substituted phenols have been described to date. In this study, one strain of microorganism that is capable of using phenol (3,000 ppm), 4-aminophenol (4,000 ppm) and 4-acetamidophenol (4,000 ppm) as sole source of carbon and energy was isolated and characterized. This strain was obtained by enrichment culture from a site contaminated with compounds like 4-acetamidophenol, 4-aminophenol and phenol in Pakistan at Bhai Pheru. The contaminated site is able to support large bacterial community as indicated by the viable cell counts (2 x 10(4) - 5 x 10(8)) per gram of soil. Detailed taxonomic studies identified the organisms as Pseudomonas species designated as strain STI. The isolate also showed growth on other organic compounds like aniline, benzene, benzyl alcohol, benzyl bromide, toluene, p-cresol, trichloroethylene and o-xylene. Optimum growth temperature and pH were found to be 30 degrees C and 7, respectively, while growth at 4, 25 and 35 degrees C and at pH 8 and 9 was also observed. Non growing suspended cells of strain ST1 degraded 68, 96 and 76.8% of 4-aminophenol (1,000 ppm), phenol (500 ppm) and 4-acetamidophenol (1,000 ppm), respectively, in 72 hrs. The isolation and characterization of Pseudomonas species strain STI, may contribute to efforts on phenolic bioremediation, particularly in an environment with very high levels of 4-acetamidophenol and 4-aminophenol.