19F NMR study on the biodegradation of fluorophenols by various Rhodococcus species

Of all NMR observable isotopes F-19 is the one perhaps most convenient for studies on biodegradation of environmental pollutants. The reasons underlying this potential of F-19 NMR are discussed and illustrated on the basis of a study on the biodegradation of fluorophenols by four Rhodococcus strains. The results indicate marked differences between the biodegradation pathways of fluorophenols among the various Rhodococcus species. This holds not only for the level and nature of the fluorinated biodegradation pathway intermediates that accumulate, but also for the regioselectivity of the initial hydroxylation step. Several of the Rhodococcus species contain a phenol hydroxylase that catalyses the oxidative defluorination of ortho-fluorinated di- and trifluorophenols. Furthermore, it is illustrated how the F-19 NMR technique can be used as a tool in the process of identification of an accumulated unknown metabolite, in this case most likely 5-fluoromaleylacetate. Altogether, the F-19 NMR technique proved valid to obtain detailed information on the microbial biodegradation pathways of fluorinated organics, but also to provide information on the specificity of enzymes generally considered unstable and, for this reason, not much studied so far.