Mineralization and transformation of monofluorophenols by Pseudonocardia benzenivorans

Abstract

The aerobic metabolism of monofluorophenols (mono-FPs) by the actinomycete, Pseudonocardia benzenivorans, was studied. This strain was able to grow on 4-fluorophenol (4-FP) and readily transform 2- and 3-fluorophenol to the corresponding metabolites. The detailed mechanism of mono-FPs degradation by P. benzenivorans was elucidated from enzymatic assays and the identification of reaction intermediates by high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry. Two types of fluorocatechols (i.e., 3- and 4-fluorocatechol) were identified as the key transformation products. During 4-FP degradation, only 4-fluorocatechol was detected, and a stoichiometric level of fluoride was released. Both fluorocatechols were observed together in cultures containing 3-fluorophenol (3-FP), while only 3-fluorocatechol was found to accumulate in 2-fluorophenol (2-FP)-containing cultures. Whole-cell extracts of P. benzenivorans expressed catechol 1,2-dioxygenase activity, indicating that the transformation of the three tested mono-FPs proceeded via ortho-cleavage pathway. The results presented in this paper provide comprehensive information regarding the metabolism of mono-FPs by a single bacterium.

The biodegradation vs. biotransformation of fluorosubstituted aromatics

“…In Pseu do noc ardia benzenivorans, 2-fluorohydroquinone was detected as an additional product (Kim et al 2010), and in R. opacus 1cp, 4-fluorocatechol was hydroxylated to form 5-fluoropyrogallol (Finkelstein et al 2000). Tyrosinase from Streptomyces antibioticus, an enzyme known to catalyze the ortho-hydroxylation of monophenols and the subsequent oxidation of diphenols to quinones, converted 3-fluorophenol into 4-fluorinated 1,2-benzoquinone which then underwent nonenzymatic polymerization reactions, thereby releasing about 50 % of the fluorine contained.…”

“…strain FP1 (Duque et al 2012) as well as in Burkholderia fungorum strain FLU100 (Strunk and Engesser 2013). Moreover, further hydroxylated by-products like fluorohydroquinone or fluoropyrogallols may be formed (Finkelstein et al 2000;Kim et al 2010).…”

“…The aromatic ring is deactivated and the electrophilic attack of molecular oxygen-the first step in most aerobic aromatic degradation pathways-generally is impaired (Guzik et al 2013). The CF 3 -group (perfluoromethyl group), however, does show a negative inductive influence only, with no positive mesomeric effect being possible (Kieltsch 2008).…”

Complete Biodegradation of 4-Fluorocinnamic Acid by a Consortium Comprising Arthrobacter sp. Strain G1 and Ralstonia sp. Strain H1

“…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).…”

“…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).…”