Cometabolic degradation of mono-chloro benzoic acids by Rhodococcus sp. R04 grown on organic carbon sources

The aerobic cometabolism of chlorobenzoic acids (CBAs) by Rhodococcus sp. R04 was accomplished by augmenting the medium with organic carbon sources. In mineral medium supplemented with glucose (MMG), 0.5 mM 2-CBA was incompletely metabolized after the 5day incubation, while the near-complete disappearance of 0.5 mM 4-CBA was monitored. Over the 5-day incubation period, the concentration of chloride increased to 0.17 mM in bottles containing 4-CBA, glucose and strain R04; whereas in cultivation with 2-CBA the chloride content was about 0.1 mM. After 5-day incubation, 28.5% 4-CBA was remained in mineral medium supplemented with ethanol (MME), and the relatively low values of chloride were released. To our knowledge, it is first report that the feasibility of using ethanol as an added substrate for cometabolic degradation of CBA by aerobic polychlorinated biphenyl (PCB)-degrading bacteria. The specific activities of (chloro)benzoate 1,2-dioxygenase and (chloro)catechol 1,2dioxygenase activities were detected in cell-free extracts (CFEs) of strain R04. These results suggest that the initial degradation of CBAs occurred most likely prior to chloride release.