Biodegradation chlorobiphenyls

Other work through the 1980s focused on the identification and characterization of various PCB degraders and included work on the biodegradation of mono-chlorobiphenyls in river water (Bailey et al., 1983), and the biodegradation of PCBs by mixed bacterial cultures grown on naphthalene and 2-methyl, 4-chloro-phenoxyacetic acid (Kilpi et al., 1988). The work of Parsons Sijm (1988) demonstrated the degradation of mono-, di- and tetrachlorobiphenyls in chemostat... 

Recently, the PCB-biodegradative capabilities of methanotrophs have been demonstrated (Adriaens, 1994). In this study, 2-CB was oxidized by a methanotrophic culture (CSC1) to a hydroxylated chlorobiphenyl intermediate identified as 2-hydroxy-3-chlorobiphenyl. This intermediate indicated that the metabolite was formed via a concerted oxidation involving an arene oxide which rearranges spontaneously via an NIH shift. No studies have shown, however, that methanotrophs can degrade more highly chlorinated PCBs, and their utility for bioremediation processes does not seem promising. 

Masse, R., Messier, F., Peloquin, L., Ayotte, C. Sylvestre, M. (1984). Microbial biodegradation of 4 chlorobiphenyl, a model compound of chlorinated biphenyls. Applied and Environmental Microbiology, 47, 947-51. 

Stolzenburg, T.R., Andren, A.W. (1983) Determination of the aqueous solubility of4-chlorobiphenyl. Anal. Chim.Acta, 151,271-274. Stucki, G., Alexander, M. (1987) Role of dissolution rate and solubility in biodegradation of aromatic compounds. Appl. Environ. Microbiol. 53, 292-297. 

Through Friedel-Crafts chlorination of biphenyl with FeCls as a catalyst, a total of 209 chlorobiphenyls can be obtained. The earlier importance of biphenyl for the production of polychlorinated biphenyls (PCB), with a chlorine content of around 50 to 55%, for plasticizers and transformer oils no longer exists today, since it was recognized in the late 1960 s that these compounds are not readily biodegradable and that their combustion at temperatures between 600 and 900 °C can release toxic dioxins. Production of polychlorinated biphenyls was therefore banned in a number of industrialized countries, e.g. in the USA in 1976. 

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