Detection of intermediate metabolites of benzene biodegradation under microaerophilic conditions

Abstract

The intermediate metabolites of benzene transformation by a microaerophilic bacterial consortium, adapted to degrade gasoline and benzene at low concentrations of dissolved oxygen (<1 mg l^-1), were identified. The examined range of initial DO concentration, 0.05 to 1 mg l^-1, was considerably lower than the previously reported values believed to be necessary to initiate benzene biodegradation. An extensive transformation of benzene, higher than the theoretical predictions for its aerobic oxidation, was observed. Phenol was identified as the most stable and the major intermediate metabolite which was subsequently transformed into catechol and benzoate. The use of ¹³C-labeled compounds identified benzene as the source of phenol, and phenol as the source of catechol and benzoate, suggesting the involvement of a monooxygenase enzymatic system in biodegradation of benzene at low DO concentrations. A metabolic sequence was proposed to describe the simultaneous detection of catechol and benzoate during the microaerophilic transformation of benzene. The results of this work demonstrate that it is possible to transform benzene, a highly carcinogenic hydrocarbon and a major contaminant of groundwater, to more easily biodegradable compounds in the presence of very small amounts of oxygen.