Enantioselective biodegradation of fluoxetine by the bacterial strain Labrys portucalensis F11

- Enantioselective degradation of fluoxetine by L. portucalensis F11 was evaluated.
- Strain F11 was able to biodegrade 2 μM of FLX as sole carbon source in 30 d.
- Degradation of 2 μM of FLX by F11 resulted in stoichiometric fluoride release.
- The supplementation with acetate resulted in increased biodegradation rate constants.
- Preferential degradation of the (R)-enantiomer over the corresponding (S)-enantiomer.

Fluoxetine (FLX) is a chiral fluorinated pharmaceutical indicated mainly for the treatment of depression and is one of the most dispensed drugs in the world. There is clear evidence of environmental contamination with this drug and its active metabolite norfluoxetine (NFLX). In this study the enantioselective biodegradation of racemic FLX and of its enantiomers by Labrys portucalensis strain F11 was assessed. When 2 μM of racemic FLX was supplemented as sole carbon source, complete removal of both enantiomers, with stoichiometric liberation of fluoride, was achieved in 30 d. For racemic FLX concentration of 4 and 9 μM, partial degradation of the enantiomers was obtained. In the presence of acetate as an additional carbon source, at 4, 9 and 21 μM of racemic FLX and at 25 μM of racemic FLX, (S)-FLX or (R)-FLX, complete degradation of the two enantiomers occurred. At higher concentrations of 45 and 89 μM of racemic FLX, partial degradation was achieved. Preferential degradation of the (R)-enantiomer was observed in all experiments. To our knowledge, this is the first time that enantioselective biodegradation of FLX by a single bacterium is reported.