Incorporation of Oxygen from Water into Toluene and Benzene during Anaerobic Fermentative Transformation

Toluene and benzene were anaerobically transformed and eventually mineralized in mixed methanogenic cultures. However, the source of oxygen for the initial oxidation step had been unknown, owing to the presence of both methanol and water. No exogenous electron acceptors other than carbon dioxide, toluene, and benzene were present in the defined mineral medium. Through the use of ¹⁸O-labeled water, the oxygen incorporated into the monoaromatic compounds was shown to come from water. The cresol from the toluene and the phenol from the benzene contained up to 8% ¹⁸O label after incubation in 9% ¹⁸O-labeled medium. Gas chromatography-mass spectrometry was used to detect the ¹⁸O-labeled aromatic metabolites.