Isolation and initial characterization of a bacterial consortium able to mineralize fluorobenzene

Abstract

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 beta-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.

FIG. 1.

Biodegradation of FB by the consortium during a batch culture at 50 mg liter⁻¹. Optical density (▵) and FB degradation based on halide release (⧫) are indicated.

FIG. 2.

Fluoride release as a consequence of FB biodegradation, versus the initial concentration of FB. The slope of the solid intercept line (slope ≅ 1.0 mM F⁻/mM FB) evidences the stoichiometric release of fluoride.

FIG. 3.

Biodegradation of FB during a fed-batch culture. Cumulative supply of FB (▪), cumulative FB degraded based on fluoride release (□), and optical density (○) are indicated.