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...