In this study, we isolated five strains capable of degrading 14 C-labeled sulfamethoxazole to 14 CO 2 from a membrane bioreactor acclimatized to sulfamethoxazole, carbamazepine, and diclofenac. Of these strains, two belonged to the phylum Actinobacteria, while three were members of the Proteobacteria.T he antibiotic sulfamethoxazole (SMX) undergoes only partial removal in municipal wastewater treatment plants (WWTP) and is often detected in treated effluents and receiving water bodies at concentrations up to 1.9 g/liter (6, 8). It is suspected to promote the development of antibacterial resistance in water bodies (3). Little information on the bacterial and fungal transformation/degradation of SMX is available. The versatile peroxidase of Bjerkandera adusta was demonstrated to transform SMX to 3-amino-5-methylisoxazole and a range of oxidation products (4). Previous studies reported the transformation of SMX by bacteria from microorganism collections. Rhodococcus rhodochrous and Pseudomonas aeruginosa were shown to cometabolize SMX (5, 7). Only Rhodococcus equi led to the transformation of SMX without glucose as a cosubstrate (7). Among the tentatively identified biotransformation products were a deamination product (5) and acetyl and hydroxyacetyl conjugates of SMX. Nevertheless, until now, no evidence for mineralization of SMX by axenic strains has been reported. This is especially important because removal of SMX can be biased by choosing unfavorable sampling conditions.In the present study, five strains capable of SMX mineralization were isolated from a lab-scale membrane bioreactor (MBR) acclimatized with a synthetic effluent loaded with pharmaceuticals. The 1.5-liter MBR was operated continuously as described in reference 1. The reactor was fed with a complex medium adapted from DIN ISO 11733 (2) and spiked with SMX, carbamazepine, and diclofenac to a final concentration of 100 g/liter (each). It was operated under steady conditions for 10 months before sampling of the biomass to inoculate enrichment cultures. The hydraulic retention time was 12 h, the sludge retention time was infinite, and the total concentration of solids was 6 g/liter, on average. At the time of biomass sampling, the average SMX removal rate in the MBR was 52% (data not shown).Enrichment cultures were prepared in Erlenmeyer flasks containing 100 ml of mineral salts medium (10) containing 0.5 mM SMX as the sole carbon source (MSM-S) and were inoculated with 2-ml samples of biomass from the MBR before incubation at 28°C on a rotary shaker at 130 rpm. Twice, after a 1-month incubation each time, half of the culture volume was replaced with fresh enriched MSM-S. After another month, 3 ml of enrichment culture was used to inoculate 100 ml of fresh MSM-S. A month later, the SMX-degrading enrichment culture was diluted in 0.85% (wt/vol) NaCl and plated on plate count agar (PCA) (medium 464; DSMZ, Germany) and, to possibly select for isolated fungi, Sabouraud agar (Sigma-Aldrich, Switzerland). Plates were incubated overnight at 28°C, and six...

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Micropollutants removal, such as pharmaceutical substances, during wastewater treatment processes is becoming a greater issue everyday. In order to optimize it, their biodegradation processes have to be better understood. So far, microcalorimetry has been used worldwide to investigate chemical reactions. For few years now it has also been developed to model and control biological processes. In the case of micropollutants, respirometry is, most of the time, not precise enough to determine biodegradation. That is why, microcalorimetric experiments have been set up. For this purpose, a 2 L Bio-RC1 (Mettler-Toledo) has been modified to reach a resolution of 5-10 mW.L(-1).In this study, the biodegradation rate of standard substrates (Ethanol and Ammonia) by an activated sludge from a full-scale CAS and one from a MBR pilot plant operating in parallel have been compared by means of microcalorimetry. Then few trials to determine the biodegradation of selected pharmaceutical substances, as well as the eventual inhibition induced by them have been made. The first results did not exhibit any biological activity. However, they have displayed inhibition for both studied substances.