Fluorinated compounds are known to be more resistant to microbial degradation than other halogenated chemicals. A microbial consortium capable of aerobic biodegradation of fluorobenzene (FB) as the sole source of carbon and energy was isolated by selective enrichment from sediments collected in a drain near an industrial site. A combination of three microbial strains recovered from the enriched consortium was shown to be necessary for complete FB mineralization. Two of the strains (F1 and F3) were classified by 16S rRNA analysis as belonging to the Sphingobacterium/Flavobacterium group, while the third (F4) falls in the ␤-Proteobacteria group, clustering with Alcaligenes species. Strain F4 was consistently found in the liquid cultures in a much greater proportion than strains F1 and F3 (86:8:6 for F4, F1, and F3, respectively). Stoichiometric release of fluoride ions was measured in batch and fed-batch cultures. In batch cultures, the consortium was able to use FB up to concentrations of 400 mg liter ؊1 and was able to utilize a range of other organic compounds, including 4-fluorophenol and 4-fluorobenzoate. To our knowledge this is the first time biodegradation of FB as a sole carbon source has been reported.The advances in organic synthesis have led to the introduction of numerous new organic compounds into the environment, whose susceptibilities to biotreatment processes are unknown. Fluoroaromatics are being increasingly used in a wide range of agrochemical and pharmaceutical products, due to the need to find environmentally acceptable alternatives to chlorinated compounds (17). The diversity of structures and the chemical inertness of many halogenated organics pose particular problems and challenges for microbial degradation (10). Some authors propose that the recalcitrance of a halogenated organic compound usually becomes greater with the increase of the electronegativity of the substituents; thus, the recalcitrance of F-C is greater than that of Cl-C, Br-C, and I-C (9).The biodegradation of a vast range of halogenated aromatic compounds, especially chlorinated compounds, has been described (13,22), but scant information is available on the metabolic and cometabolic fate of fluorinated aromatic compounds in bacteria. Examples of biodegradation of fluorinated compounds most commonly found in the literature involve fluorobenzoic acids (7,15,20,21,24) and fluorophenols (1, 2, 23). Although degradation under aerobic conditions is usually reported, anaerobic degradation of fluorobenzoates under denitrifying conditions has also been reported (26). The existence of various metabolic pathways, some of which may lead to the formation of inhibitor metabolites, has been reported (15,24,25). In some cases, as in the degradation of fluoroacetate, a specific enzyme is responsible for the cleavage of the C-F bond (12). Studies on the metabolism of 2-flurobenzoate have shown that cleavage of the C-F bond occurs incidentally during oxygenase attack on the aromatic ring (20). It has been reported that biodegradation of fluo...

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The aerobic metabolism of fluorobenzene by Rhizobiales sp. strain F11 was investigated. Liquid chromatography-mass spectrometry analysis showed that 4-fluorocatechol and catechol were formed as intermediates during fluorobenzene degradation by cell suspensions. Both these compounds, unlike 3-fluorocatechol, supported growth and oxygen uptake. Cells grown on fluorobenzene contained enzymes for the ortho pathway but not for meta ring cleavage of catechols. The results suggest that fluorobenzene is predominantly degraded via 4-fluorocatechol with subsequent ortho cleavage and also partially via catechol.During the last decades, environmental contamination by fluorinated organic compounds has received increasing attention because of their use as herbicides, fungicides, surfactants, refrigerants, intermediates in organic synthesis, solvents, and pharmaceuticals (11). Whereas the biodegradation of chlorinated compounds has been studied quite extensively (19), little is known about the bacterial metabolism of fluoroaromatic compounds, even though there have been several reports on the degradation of fluorobenzoic acids (5,6,7,16). With chloroaromatics, most degradation routes involve dioxygenase-and dehydrogenase-mediated conversion to the corresponding chlorocatechols, which are further metabolized by a dioxygenase that cleaves the aromatic ring. Dehalogenation occurs during metabolism of the ring-cleavage products (19). Most described strains degrade chlorocatechols via the ortho-cleavage pathway (14,18,19,20), but meta cleavage of 3-chlorocatechol can also occur (13), even though the meta-cleavage route is often unproductive due to the formation of toxic or dead-end products (1,19). Dehalogenation may in some cases occur prior to ring cleavage. For example, mutants of Pseudomonas sp. strain B13 and Alcaligenes eutrophus B9 that grow on 2-fluorobenzoate use a dioxygenase to convert it to catechol, with concomitant decarboxylation and defluorination (5). Pseudomonas putida strain CLB 250, which can use three different 2-halobenzoates, also converts these substrates by initial dehalogenating dioxygenation (6), and a defluorinating 4-fluorobenzoate monooxygenase has been reported as well (16).The present paper describes a metabolic pathway for fluorobenzene (FB). Information about the bacterial metabolism of this compound is scarce, despite studies on its chlorinated analogue (13, 18). Lynch et al. (12) described the oxidation of FB to 3-fluorocatechol by a strain of Pseudomonas putida, but in this study FB was not used as a carbon source. Recently, FB was reported to be completely degraded by a bacterial consortium (2) and by a pure bacterial culture that utilized it as a sole carbon and energy source (3). This gram-negative bacterium, phylogenetically classified within the order Rhizobiales, was named strain F11 and was used here to investigate the metabolism of FB.Intermediates produced during FB degradation. In order to obtain information about the degradation pathway of FB, we tested which intermediates accumulated...

Fluorinated organic compounds are of growing industrial importance, with applications such as agrochemicals, pharmaceuticals, and performance materials (23,24,28,41). The safe use of such compounds, as well as appropriate disposal and treatment of wastes, will benefit from knowledge about their biodegradation. However, little information is available about the microbial metabolism of fluorinated organic compounds compared to other halogenated chemicals. Most studies on the bacterial degradation of fluorinated organics describe fluorobenzoic acids, which under aerobic conditions can be converted into the corresponding fluorocatechols (3, 17, 33). Papers about the degradation of fluorophenols have also appeared (11,25,51).4-Fluorocinnamic acid (4-FCA) is used in industry for the synthesis of flavors and pharmaceuticals (8), and polymers of 4-FCA are applied in electronics (14). It was proposed that under aerobic conditions in nonacclimated industrial activated sludge, 4-FCA could be converted into 4-fluorobenzoic acid (4-FBA) via the formation of 4-fluoroacetophenone (4-FAP) (8, 32). In another study, using activated sludge from a wastewater treatment plant, 4-FCA was suggested to be transformed into an epoxide that is converted to 4-FAP. This compound would then be converted into 4-FBA, but no products were detected from the breakdown of 4-FBA (5).The conversion of nonhalogenated cinnamic acids to benzoic acids, such as the transformation of ferulic acid to vanillic acid, has been described previously (2,4,20,31,39). Cinnamic acid, coumaric acid, and ferulic acid are transformed by Streptomyces setonii (47) and Rhodopseudomonas palustris to benzoic acid or the corresponding derivatives (19). Alcanivorax borkumensis MBIC 4326 (9) and Papillibacter cinnamivorans (7) transformed cinnamic acid into benzoic acid. The metabolism of these compounds thus proceeds with side chain degradation prior to ring cleavage. Side chain degradation is carried out either by ␤-oxidation or by direct deacetylation mechanisms, which leads to elimination of two carbon units from the unsaturated side chain in bacteria, yeasts, and fungi (40).Since no clear information on the degradation route of 4-FCA is available, we have isolated two pure bacterial strains to study the complete microbial metabolism of the compound, and in this paper, we propose a degradation pathway. MATERIALS AND METHODSGrowth conditions. Cells of strains G1 and H1 were grown aerobically at 30°C under rotary shaking or in a fermentor. Growth medium (MMY) contained (per liter) 5.37 g of Na 2 HPO 4 ⅐ 12H 2 O, 1.36 g of KH 2 PO 4 , 0.5 g of (NH 4 ) 2 SO 4 , and 0. Enrichment and isolation of 4-FCA-and 4-FBA-degrading organisms. Soil samples collected from a site in the Netherlands contaminated mainly with chlorobenzene and halogenated aliphatic compounds were used as the initial inocula for the 4-FCA and 4-FBA enrichment cultures. Flasks contained 40 ml MMY and 5 mM 4-FCA or 5 mM 4-FBA as the sole source of carbon and energy. The cultures were incubated at room temperatur...

The aerobic metabolism of fluorobenzene by Rhizobiales sp. strain F11 was investigated. Liquid chromatography-mass spectrometry analysis showed that 4-fluorocatechol and catechol were formed as intermediates during fluorobenzene degradation by cell suspensions. Both these compounds, unlike 3-fluorocatechol, supported growth and oxygen uptake. Cells grown on fluorobenzene contained enzymes for the ortho pathway but not for meta ring cleavage of catechols. The results suggest that fluorobenzene is predominantly degraded via 4-fluorocatechol with subsequent ortho cleavage and also partially via catechol.During the last decades, environmental contamination by fluorinated organic compounds has received increasing attention because of their use as herbicides, fungicides, surfactants, refrigerants, intermediates in organic synthesis, solvents, and pharmaceuticals (11). Whereas the biodegradation of chlorinated compounds has been studied quite extensively (19), little is known about the bacterial metabolism of fluoroaromatic compounds, even though there have been several reports on the degradation of fluorobenzoic acids (5,6,7,16). With chloroaromatics, most degradation routes involve dioxygenase-and dehydrogenase-mediated conversion to the corresponding chlorocatechols, which are further metabolized by a dioxygenase that cleaves the aromatic ring. Dehalogenation occurs during metabolism of the ring-cleavage products (19). Most described strains degrade chlorocatechols via the ortho-cleavage pathway (14,18,19,20), but meta cleavage of 3-chlorocatechol can also occur (13), even though the meta-cleavage route is often unproductive due to the formation of toxic or dead-end products (1,19). Dehalogenation may in some cases occur prior to ring cleavage. For example, mutants of Pseudomonas sp. strain B13 and Alcaligenes eutrophus B9 that grow on 2-fluorobenzoate use a dioxygenase to convert it to catechol, with concomitant decarboxylation and defluorination (5). Pseudomonas putida strain CLB 250, which can use three different 2-halobenzoates, also converts these substrates by initial dehalogenating dioxygenation (6), and a defluorinating 4-fluorobenzoate monooxygenase has been reported as well (16).The present paper describes a metabolic pathway for fluorobenzene (FB). Information about the bacterial metabolism of this compound is scarce, despite studies on its chlorinated analogue (13, 18). Lynch et al. (12) described the oxidation of FB to 3-fluorocatechol by a strain of Pseudomonas putida, but in this study FB was not used as a carbon source. Recently, FB was reported to be completely degraded by a bacterial consortium (2) and by a pure bacterial culture that utilized it as a sole carbon and energy source (3). This gram-negative bacterium, phylogenetically classified within the order Rhizobiales, was named strain F11 and was used here to investigate the metabolism of FB.Intermediates produced during FB degradation. In order to obtain information about the degradation pathway of FB, we tested which intermediates accumulated...