Biodegradation of p-nitrophenol by Pseudomonas aeruginosa HS-D38 and analysis of metabolites with HPLC–ESI/MS

Pseudomonas aeruginosa strain HS-D38 was capable of mineralizing p-nitrophenol (PNP) as the sole source of carbon, nitrogen and energy. Degradation of 200 mg L−1 PNP was examined in different media including: (i) MSM (mineral salts medium, no carbon and nitrogen source); (ii) addition of 1% ammonium chloride as additional nitrogen source (ANM); and (iii) addition of 1% glucose as a carbon source (ACM). Complete degradation of 200 mg L−1 PNP was achieved in 12 h in MSM. Additional ammonium chloride accelerated the PNP degradation, but additional glucose inhibited this process. This strain metabolized as high concentration as 300 and 500 mg L−1 of PNP in 14 h and 24 h, respectively, in MSM. The degradation was accompanied by release of stoichiometric amount of nitrate from PNP. During the bacterial growth on PNP, hydroquinone and 1,2,4-benzenetriol were observed as the key degradation intermediates by using a combination of techniques, including HPLC–DAD and LC–ESI/MS compared with the authentic standards. These results indicated that PNP was degraded via a hydroquinone pathway.