Continuous treatment of clofibric acid by Trametes versicolor in a fluidized bed bioreactor: Identification of transformation products and toxicity assessment

• Trametes versicolor is capable of degrading CLOF in liquid medium.
• In continuous mode at 4 d HRT, 80% of the influent concentration was reduced.
• Hydroxy-CLOF was identified as major metabolite confirming the degradation of CLOF.
• In batch treatment the non-degradability of hydroxy-CLOF was demonstrated.
• Acute toxicity tests showed that final effluents of the reactors were not toxic but more toxic than the beginning.

The aerobic degradation of the blood lipid regulator clofibric acid (CLOF) was studied in a continuous bioreactor treatment using the white-rot fungus Trametes versicolor. Experiments in Erlenmeyer flasks with the compound at 30 μg L−1 showed that CLOF can be completely degraded at near environmentally relevant concentration after 4 days. The degradation process was scaled-up in an air-pulsed fluidized bioreactor operated in continuous mode with a hydraulic retention time of 4 days. The results show that 80% of the fed concentration (160 μg L−1) was reduced at the steady state (from day 12 to the end). Here, CLOF removal rate was 12.5 μg g−1 dry weight biomass d−1. The 2-(4-chlorophenoxy)-2-(hydroxymethyl)propanoic acid (hydroxy-CLOF) was identified as major metabolite, confirming the degradation of CLOF, but its concentration remained constant in the medium. In addition, in a batch bioreactor treatment the undegradability of hydroxy-CLOF was demonstrated. Finally, acute toxicity tests (Microtox) performed with the bacterium Vibrio fischeri showed that the final culture broth in both batch (15 min EC50 of 55%) and continuous (11%) experiments were more toxic than the beginning (61%).

Figure optionsDownload as PowerPoint slide