Aerobic degradation study of three fluoroanilines and microbial community analysis: the effects of increased fluorine substitution

Abstract

The fate of fluorinated compounds in the environment, especially polyfluorinated aromatics, is a matter of great concern. In this work, 4-Fluoroaniline (4-FA), 2,4-Difluoroanilines (2,4-DFA), and 2,3,4-Trifluoroanilines (2,3,4-TFA), were chosen as the target pollutants to study their biodegradability under aerobic conditions. The required enriched time of the mixed bacterial culture for degrading 4-FA, 2,4-DFA, and 2,3,4-TFA was 26, 51, and 165 days, respectively, which suggested that the longer enrichment time was required with the increase of fluorine substitution. At the initial concentrations of 100-200 mg L(-1), the 4-FA, 2,4-DFA, and 2,3,4-TFA could be degraded completely by the mixed bacterial culture. The maximum specific degradation rates of 4-FA, 2,4-DFA, and 2,3,4-TFA were 22.48 ± 0.55, 15.27 ± 2.04, and 8.84 ± 0.93 mg FA (g VSS h)(-1), respectively. Also, the three FAs enriched cultures showed certain potential of degrading other two FAs. The results from enzyme assay suggested the expression of meta-cleavage pathways during three FAs degradation. The denaturing gradient gel electrophoresis analysis revealed that unique bacterial communities were formed after FAs enrichment and these were principally composed of β-Proteobacteria, Oscillatoriophycideae, δ-Proteobacteria, α-Proteobacteria, Thermales, Xanthomonadales, Deinococci, Flavobacteriia, and Actinobacteridae. The Shannon-Wiener indexes in three FAs enriched culture decreased with the increase of fluorine substitution, indicating the significant effect of fluorine substitution on the microbial diversity. These findings supply important information on the fate of three FAs under aerobic environment, and the bacterial communities in their degradation systems.

The biodegradation vs. biotransformation of fluorosubstituted aromatics

“…This strain converted 2,4-and 3,4-difluoroanilines and 2,3,4-trifluoroaniline cometabolically with 4-fluoroaniline . Only meta pyrocatechase activity was found in mixed cultures enriched from activated sludge after growth with 2,4-difluoroaniline and 2,3,4-trifluoroaniline as well (Zhao et al 2015).…”

“…Further degradation of 4-chlorocatechol proceeded via ortho cleavage of the aromatic ring in both cases. Although meta fission of halogenated catechols may produce toxic dead-end products, meta pyrocatechase activity was found to predominate in a number of fluoroanilinedegrading cultures (Zhang et al 2014;Zhao et al 2015). Ralstonia sp.…”

“…Growth with 4-fluoroaniline was further reported for Moraxella sp. strain G (Zeyer et al 1985) and a mixed culture which had been enriched using sucrose as an additional carbon source (Zhao et al 2015).…”