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- Co-metabolic degradation of chlorobenzene by the fluorobenzene degrading wild strain Labrys portucalensisPublication . Moreira, Irina S.; Amorim, Catarina L.; Carvalho, Maria F.; Castro, Paula M.L.Due to the widespread use of chlorobenzene (CB), environmental contamination with this compound is a major concern. A previously isolated bacterium named Labrys portucalensis (strain F11), that is able to use fluorobenzene (FB) as sole carbon and energy source, was tested for its capability to degrade CB. Strain F11 was able to partially degrade CB only when F11 cells were previously grown in FB. Biodegradation of 0.5 mM of CB was achieved at a rate of 7.95 0.39 mmol l 1 day 1 with concomitant stoichiometric release of 50% of the chloride, while degradation of 1 mM of this compound resulted in 85% degradation at a rate of 16.9 0.81 mmol l 1 day 1 and with a 15% chloride release on the basis of the amount of compound biodegraded. Total CB biodegradation and dechlorination was only achieved when FB was also supplied to F11 cultures, suggesting cometabolic transformation. Total degradation of 0.5 mM of CB and 0.5 mM of FB occurred simultaneously at degradation rates of 105 6.07 mmol l 1 day 1 and 126 16.2 mmol l 1 day 1 respectively, with stoichiometric halogen release. Growth yield was lower when both substrates were present, suggesting synergistic inhibition. To our knowledge, this is the first time that co-metabolic biodegradation of CB in the presence of the fluorinated analogue is reported.
- Effect of the metals iron, copper and silver on fluorobenzene biodegradation by Labrys portucalensisPublication . Moreira, Irina S.; Amorim, Catarina L.; Carvalho, Maria F.; Ferreira, António C.; Afonso, Carlos M.; Castro, Paula M. L.Organic and metallic pollutants are ubiquitous in the environment. Many metals are reported to be toxic to microorganisms and to inhibit biodegradation. The effect of the metals iron, copper and silver on the metabolism of Labrys portucalensis F11 and on fluorobenzene (FB) biodegradation was examined. The results indicate that the addition of 1 mM of Fe2+ to the culture medium has a positive effect on bacterial growth and has no impact in the biodegradation of 1 and 2 mM of FB. The presence of 1 mM of Cu2+ was found to strongly inhibit the growth of F11 cultures and to reduce the biodegradation of 1 and 2 mM of FB to ca. 50 %, with 80 % of stoichiometrically expected fluoride released. In the experiments with resting cells, the FB degraded (from 2 mM supplied) was reduced ca. 20 % whereas the fluoride released was reduced to 45 % of that stoichiometrically expected. Ag+ was the most potent inhibitor of FB degradation. In experiments with growing cells, the addition of 1 mM of Ag+ to the culture medium containing 1 and 2 mM of FB resulted in no fluoride release, whereas FB degradation was only one third of that observed in control cultures. In the experiments with resting cells, the addition of Ag+ resulted in 25 % reduction in substrate degradation and fluoride release was only 20 % of that stoichiometrically expected. The accumulation of catechol and 4-fluorocatechol in cultures supplemented with Cu2+ or Ag+ suggest inhibition of the key enzyme of FB metabolism-catechol 1,2-dioxygenase.
- Degradation of difluorobenzenes by the wild strain Labrys portucalensisPublication . Moreira, Irina S.; Amorim, Catarina L.; Carvalho, Maria F.; Castro, Paula M. L.This study focuses on the biodegradation of difluorobenzenes (DFBs), compounds commonly used as intermediates in the industrial synthesis of various pharmaceutical and agricultural chemicals. A previously isolated microbial strain (strain F11), identified as Labrys portucalensis, able to degrade fluorobenzene (FB) as sole carbon and energy source, was tested for its capability to degrade 1,2-, 1,3- and 1,4-DFB in batch cultures. Strain F11 could use 1,3-DFB as a sole carbon and energy source, with quantitative release of fluoride, but 1,4-DFB was only degraded and defluorinated when FB was supplied simultaneously. Growth of strain F11 with 0.5 mM of 1,3-DFB led to stoichiometric release of fluoride ion. The same result was obtained in cultures fed with 1 mM of 1,3-DFB or 0.5 mM of 1,4-DFB, in the presence of 1 mM of FB. No growth occurred with 1,2-DFB as substrate, and degradation of FB was inhibited when supplied simultaneously with 1,2-DFB. To our knowledge, this is the first time biodegradation of 1,3-DFB as a sole carbon and energy source, and cometabolic degradation of 1,4- DFB, by a single bacterium, is reported.