Transformation of bisphenol A and alkylphenols by ammonia-oxidizing bacteria through nitration.

Transformation of bisphenol A (BPA) by ammonia-oxidizing bacteria (AOB) Nitrosomonas europaea ATCC 19718 was investigated. On the basis of the ultraperformance liquid chromatography (UPLC) coupled to quadrupole time-of-flight mass spectrometry (Q-TOF MS) and nuclear magnetic resonance analysis, we found N. europaea could transform BPA into nitro- and dinitro-BPA, suggesting that abiotic nitration between the biogenic nitrite and BPA played a major role in the transformation of BPA in the batch AOB system. Nitrite concentrations, temperature, and pH values were the major factors to influence the reaction rate. Furthermore, the yeast estrogenic screening assay showed that the formed nitro- and dinitro-BPA had much less estrogenic activity as compared with its parent compound BPA. Similar reactions of abiotic nitration were considered for 4-n-nonylphenol (nNP) and 4-n-octylphenol (nOP) since nitro-nNP and nitro-nOP were detected by UPLC-Q-TOF MS. In addition, results from the local wastewater treatment plant (WWTP) showed the occurrence of nitro-BPA and dinitro-BPA during the biological treatment process and in the effluent, indicating that nitration of BPA is also a pathway for removal of BPA. Results of this study provided implication that AOB in the WWTPs might contribute to removal of selected endocrine-disrupting compounds (EDCs) through abiotic nitritation.