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Research Project
MICROBIAL DEGRADATION OF FLUORINATED COMPOUNDS - STUDIES ON BIODEGRADATION MECHANISMS AND BIOTREATMENT SYSTEMS
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Publications
Mineralization of 4-fluorocinnamic acid by a Rhodococcus strain
Publication . Amorim, Catarina L.; Ferreira, António César Silva; Carvalho, M.F.; Afonso, Carlos M. M.; Castro, Paula M.L.
A bacterial strain capable of aerobic degradation of
4-fluorocinnamic acid (4-FCA) as the sole source of carbon
and energy was isolated from a biofilm reactor operating for
the treatment of 2-fluorophenol. The organism, designated as
strain S2, was identified by 16S rRNA gene analysis as a
member of the genus Rhodococcus. Strain S2 was able to
mineralize 4-FCA as sole carbon and energy source. In the
presence of a conventional carbon source (sodium acetate
[SA]), growth rate of strain S2 was enhanced from 0.04 to
0.14 h−1 when the culture medium was fed with 0.5 mMof 4-
FCA, and the time for complete removal of 4-FCA decreased
from 216 to 50 h.When grown in SA-supplemented medium,
4-FCA concentrations up to 1 mM did not affect the length of
the lag phase, and for 4-FCA concentrations up to 3 mM,
strain S2 was able to completely remove the target fluorinated
compound. 4-Fluorobenzoate (4-FBA) was transiently formed
in the culture medium, reaching concentrations up to 1.7 mM
when the cultures were supplemented with 3.5mMof 4-FCA.
Trans,trans-muconate was also transiently formed as a metabolic
intermediate. Compounds with molecular mass compatible
with 3-carboxymuconate and 3-oxoadipate were also
detected in the culture medium. Strain S2 was able to mineralize
a range of other haloorganic compounds, including 2-
fluorophenol, to which the biofilm reactor had been exposed.
To our knowledge, this is the first time that mineralization of 4-FCA as the sole carbon source by a single bacterial culture is
reported.
Biodegradation of ofloxacin, norfloxacin, and ciprofloxacin as single and mixed substrates by Labrys portucalensis F11
Publication . Amorim, Catarina L.; Moreira, Irina S.; Maia, Alexandra S.; Tiritan, Maria E.; Castro, Paula M. L.
Fluoroquinolone (FQ) antibiotics are extensively
used both in human and veterinary medicine, and their
accumulation in the environment is causing an increasing
concern. In this study, the biodegradation of the three most
worldwide used FQs, namely ofloxacin, norfloxacin, and
ciprofloxacin, by the fluoroorganic-degrading strain Labrys
portucalensis F11 was assessed. Degradation occurred when
the FQs were supplied individually or as mixture in the culture
medium, in the presence of an easily degradable carbon
source. Consumption of individual FQs was achieved at
different extents depending on its initial concentration,
ranging from 0.8 to 30 μM. For the lowest concentration, total
uptake of each FQ was observed but stoichiometric fluoride
release was not achieved. Intermediate compounds were
detected and identified by LC-MS/MS with a quadrupole time
of flight detector analyzer. Biotransformation of FQs by L.
portucalensis mainly occurred through a cleavage of the piperazine ring and displacement of the fluorine substituent
allowing the formation of intermediates with less antibacterial
potency. FQ-degrading microorganisms could be useful for
application in bioaugmentation processes towards more
efficient removal of contaminants in wastewater treatment
plants.
Biodegradation of fluoroanilines by the wild strain Labrys portucalensis
Publication . Amorim, Catarina L.; Carvalho, Maria F.; Afonso, Carlos M. M.; Castro, Paula M. L.
Aniline and halogenated anilines are known as widespread environmental toxic pollutants released into soil and water. In contrast to aniline, which is rapidly metabolized via catechol, halosubstituted anilines are more resistant to microbial attack. A fluorobenzene-degrading bacterium, Labrys portucalensis strain F11, was tested under different culture conditions for the degradation potential towards 2-, 3- and 4-fluoroaniline (2-, 3- and 4-FA). Strain F11 was able to use FAs as a source of carbon and nitrogen however, supplementation with a nitrogen source improved substrate consumption and its dehalogenation extent. When F11 cells were previously grown on fluorobenzene (FB), higher biodegradation rates were achieved for all isomers. Complete 2-FA biodegradation with stoichiometric fluoride release was achieved when FB-induced cells were used. On the other hand, the degradation of 3- and 4-FA was characterized by incomplete defluorination of the target compounds suggesting accumulation of fluorinated intermediates. F11 cultures simultaneously supplied with FB and the fluorinated anilines showed a concomitant degradation of both substrates, suggesting co-metabolic biodegradation. To our knowledge, this is the first time that biodegradation of 2- and 3-FA as a sole carbon and nitrogen source and co-metabolic degradation of FA isomers in the presence of a structural analogous compound is reported.
Performance of aerobic granular sludge in a sequencing batch bioreactor exposed to ofloxacin, norfloxacin and ciprofloxacin
Publication . Amorim, Catarina L.; Maia, Alexandra S.; Mesquita, Raquel B. R.; Rangel, António O.S.S.; Loosdrecht, Mark C.M. van; Tiritan, Maria Elizabeth; Castro, Paula M.L.
A granular sludge sequencing batch reactor (SBR) was operated for 340 days for treating a
synthetic wastewater containing fluoroquinolones (FQs), namely ofloxacin, norfloxacin
and ciprofloxacin. The SBR was intermittently fed with FQs, at concentrations of 9 and
32 mM. No evidence of FQ biodegradation was observed but the pharmaceutical compounds
adsorbed to the aerobic granular sludge, being gradually released into the medium in
successive cycles after stopping the FQ feeding.
Overall COD removal was not affected during the shock loadings. Activity of ammonia
oxidizing bacteria and nitrite oxidizing bacteria did not seemto be inhibited by the presence of
FQs (maximum of 0.03 and 0.01 mM for ammonium and nitrite in the effluent, respectively).
However, during the FQs feeding, nitrate accumulation up to 1.7 mM was observed at the
effluent suggesting that denitrificationwas inhibited. The activity of phosphate accumulating
organismswas affected, as indicated by the decrease of P removal capacity during the aerobic
phase. Exposure to the FQs also promoted disintegration of the granules leading to an increase
of the effluent solid content, nevertheless the solid content at the bioreactor effluent returned
to normal levelswithin ca. 1month after removing the FQs in the feed allowing recovery of the
bedvolume. Denaturing gradient gel electrophoresis revealed a dynamic bacterial community
with gradual changes due to FQs exposure. Bacterial isolates retrieved from the granules
predominantly belonged to a- and g-branch of the Proteobacteria phylum.
Bioaugmentation for treating transient 4-fluorocinnamic acid shock loads in a rotating biological contactor
Publication . Amorim, Catarina L.; Duque, Anouk F.; Afonso, Carlos M. M.; Castro, Paula M. L.
A rotating biological contactor (RBC) was used to treat shock loadings of 4-fluorocinnamic acid (4-FCA). Intermittent 4-FCA shocks of 35 mg L-1 were applied (ca. 3 months) with only limited mineralization occurring and accumulation of 4-fluorobenzoate (4-FBA) as an intermediate. After bioaugmentation with a degrading bacterium the RBC was able to deal with 4-FCA intermittent loading of 80 mg L-1 however, a gradual decline in RBC performance occurred, leading to 4-FBA accumulation. The degrading strain was recovered from the biofilm during 2 months but intermittent feeding may have led to diminishing strain numbers. Distinct bacterial communities in the 1st and the 5th and 10th stages of the RBC were revealed by denaturating gradient gel electrophoresis. Several isolates retrieved from the RBC transformed 4-FCA into 4-FBA but only two strains mineralized the compound. Bioaugmentation allowed removal of the fluorinated compound however intermittent feeding may have compromised the bioreactor efficiency.
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Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
Funding Award Number
SFRH/BD/47109/2008