4- chlorobenzoate aerobic degradation

Aerobic degradation of chlorinated arene hydrocarbons, including the important group PCBs, and chlorobenzoates that are produced from them as metabolites, is generally initiated by dihy-droxylation of the rings to dihydrodiols followed by dehydrogenation to catechols. Halide may be lost simultaneously and for 2-halogenated benzoates, both halide and carboxyl. Salient aspects are summarized, and attention drawn to selected aspects of enzyme inhibition. 

Other componnds have also been examined as primers for the dechlorination of hexachloro to nonachloro PCB congeners (DeWeerd and Bedard 1999) a nnmber of snbstituted brominated monocyclic aromatic componnds were examined, and 4-bromobenzoate was effective—though less so than 2,6-dibromobiphenyl. In contrast, the chlorobenzoates that are metabolites of aerobic degradation were ineffective. The positive effect of brominated biphenyls in priming the anaerobic dechlorination of CBs has also been encountered in the dechlorination of octachlorodibenzo[l,4] dioxin to the 2,3,7,8 congener indnced by 2-bromodibenzo[l,4]dioxin in the presence of (Albrecht... 

Chlorobenzoates may be formed during the initial steps in the aerobic degradation of PCBs, and their further metabolism illustrates a number of pathways. There are several reactions that carry out dehalogenation including dioxygenation, hydrolysis, and reduction. 

Krooneman J, ERB Moore, JCL van Velzen, RA Prins, LJ Forney, JC Gottschal (1998) Competition for oxygen and 3-chlorobenzoate between two aerobic bacteria using different degradation pathways. EEMS Microbiol Ecol 26 171-179. 

Analysis of chlorobenzoates in sediments, which had been contaminated with PCBs, was used to demonstrate that the lower PCB congeners that had initially been produced by anaerobic dechlorination were subsequently degraded under aerobic conditions. The chlorobenzoates were transient metabolites and their concentrations were extremely low since bacteria that could successfully degrade them were present in the sediment samples (Elanagan and May 1993). 

Fava F, Di Gioia D, Marchetti L, et al. 1993. Aerobic mineralization of chlorobenzoates by a natural polychlorinated biphenyl-degrading mixed bacterial culture. Appl Microbiol Biotechnol 40(4) 541-548. 

Chlorinated benzoic acids have been shown to be intermediates in the biodegradation of several chlorinated aromatic compounds, for example, 4-chlorobenzoic acid is formed in the biodegradation of both polychlorinated biphenyls [103]. Mixed microbial cultures, which have been studied by a number of groups under aerobic conditions, can degrade a wide range of chlorinated benzoic acids, including 2-, 3- and 4-chlorobenzoic acid as well as 3,4-dichloro- and 2,4-dichlorobenzoic acid [104]. By contrast, under anaerobic conditions, only reductive dechlorination of meta-substituted benzoic acids has been observed [49,105,106]. Cometabolism of chlorobenzoic acids in the presence of unsubstituted benzoic adds leads to the formation of the corresponding... 

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