Biofilm-catalysed transformation of organofluorine compounds
Biofilms are microorganisms immobilised to a surface, surrounded by a matrix consisting of polysaccharide, protein and/or nucleic acid, forming a dynamic, yet stable, structure. This stability means that biofilms are more resistant to xenobiotic compounds, and are metabolically active for extended time periods. These properties make biofilms difficult to treat in clinical situations, but potentially useful in biocatalysis and bioremediation. In this paper the application of biofilms to the biodegradation and biotransformation of organofluorine compounds will be discussed.
MICROBIAL TRANSFORMATION OF ORGANOFLUORINE COMPOUNDS
Fluorine’s importance in the manufacture of a range of useful compounds, including pharmaceuticals, agrochemicals, solvents, refrigerants, etc., is well established (1). Microorganisms are known to transform, degrade and biosynthesise organofluorine compounds (Scheme 1). From an environmental perspective, the stability of the C-F bond makes organofluorine compounds difficult to degrade, yet some microorganisms are capable of employing compounds such as fluoroacetate, fluorobenzoate, fluorophenol and fluorobiphenyl as carbon and energy sources (2). The ability of bacteria, belonging mainly to the genera Pseudomonas, Sphingomonas and Rhodococcus, to degrade fluoroaryl compounds stems from the specificity of the enzymes involved in catabolism of aromatic compounds, which can accept fluorinated intermediates as substrates. The fluorinated compounds are transformed via oxygenases, either yielding fluorinated dead-end products, such as 3-fluoromuconic acid, or are converted to an unstable fluorinated intermediate, from which fluoride ion is spontaneously eliminated. Only one class of enzyme, fluoroacetate ...