[Isolation and characterization of a halotolerant p-nitroaniline degrading strain S8]

A bacterial strain S8 was isolated from pesticide-contaminated sludge, which showed ability of utilizing p-nitroaniline as the sole source of carbon and nitrogen for growth. Based on the morphology, the physiological and biochemical characteristics, and the 16S rDNA sequence analysis, the strain was identified as Bacillus subtilis. Strain S8 showed high efficiency in p-nitroaniline degradation. 65.6% and 55.8% of p-nitroaniline (60 mg x L(-1) and 120 mg x L(-1)) were degraded by this strain within 72 hours under the optimal conditions of 31degrees C and pH 6.0. Besides, strain S8 degraded 49.5% p-nitroaniline in 7% NaCl and 27.4% p-nitroaniline in 10% NaCl (72 h), which showed that the strain S8 had a high salinity tolerance. When the LC-MS method was used for identification of the biodegradation products, six kinds of degradation products were found, two of which were identified as phenol and hydroquinone. To date, this is the first report on the degradation of p-nitroaniline by Bacillus subtilis. These results suggest that S8 could be a potential candidate for treating p-nitroaniline-contaminated saline wastewater.