Bioremediation of bezafibrate and paroxetine by microorganisms from estuarine sediment and activated sludge of an associated wastewater treatment plant.

The present work aimed to explore the potential of autochthonous microorganisms from an urban estuary and from activated sludge of an associated wastewater treatment plant (WWTP), for biodegradation of an antidepressant drug, paroxetine, and on a cholesterol-lowering agent, bezafibrate. These compounds were chosen as representatives of extensively used pharmaceuticals. Autochthonous microorganisms from the indicated sources were exposed to the target pharmaceuticals (1 mg/L) in co-metabolism with sodium acetate (500 mg/L) along a two-weeks period, for a total of 7 two-weeks periods (here referred as cycles). Exposures were carried out in batch mode, under different incubation conditions (agitation vs. static). Removal of pharmaceuticals was monitored at the end of each cycle, by analysing the culture medium. For paroxetine, fluoride ion release was also followed as an indicator of defluorination of the molecule. The structure of the bacterial communities was analysed by ARISA (Automated rRNA Intergenic Spacer Analysis), at the beginning of the experiment and at the end of the first and the last cycles to identify substantial changes associated with the time of exposure, the incubation conditions and the presence and type of pharmaceuticals. Incubation conditions affected not only the bacterial community structure, but also the biodegradation efficiency. At the beginning of the experiment, removal of target pharmaceuticals was found to be lower under agitation than under static conditions, but at the end of the experiment, results showed high removal of the pharmaceuticals from the culture medium (>97%) under both conditions, mainly by microbiological processes. For paroxetine, adsorption and abiotic processes also had an important influence on its removal, but defluorination only occurred in the presence of microorganisms. These results highlight that autochthonous microorganisms from estuarine sediments and WWTP sludge have high ability to remove the selected pharmaceuticals with relevant implications for the development of new bioremediation tools for environmental restoration.

Removal of naproxen and bezafibrate by activated sludge under aerobic conditions: kinetics and effect of substrates.

Naproxen and bezafibrate fall into the category of pharmaceuticals that have been widely detected in the aquatic environment, and one of the major sources is the effluent discharge from wastewater treatment plants. This study investigated the sorption and degradation kinetics of naproxen and bezafibrate in the presence of activated sludge under aerobic conditions. Experimental results indicated that the adsorption of pharmaceuticals by activated sludge was rapid, and the relative adsorbabilities of the two-target compounds were based on their log Kow and pKa values. The adsorption data could be well interpreted by the pseudo-second-order kinetic model. The degradation process could be described by the pseudo-first-order kinetic model, whereas the pseudo-second-order kinetics were also well suited to describe the degradation process of the selected compounds at low concentrations. Bezafibrate was more easily degraded by activated sludge compared with naproxen. The spiked concentration of the two-target compounds was negatively correlated with k1 and k2s , indicating that the substrate inhibition effect occurred at the range of studied concentrations. Chemical oxygen demand (COD) did not associate with naproxen degradation; thus, COD is not an alternative method that could be applied to investigate natural organic matter's impact on degradation of pharmaceuticals by activated sludge.

Radioautographic study on the intracellular localization of a hypolipidemic agent, bezafibrate, a peroxisome proliferator, in cultured rat hepatocytes.

In order to demonstrate the intracellular localization of the peroxisome proliferator in the hepatocytes, we have examined the localization of silver grains due to 14C-labelled bezafibrate in cultured rat hepatocytes by means of light and electron microscopic radioautography. As it results from the difference between chemical fixation and freeze-substitution by light microscopic radioautography, more numerous silver grains, about twice, were observed in freeze-substitution specimens in comparison with chemical fixation. On light microscopic radioautograms of the epoxy resin sections during each experimental condition, about 90% of all the silver grains were localized over the cytoplasm. Then, statistical significance was evaluated on grain density in the cytoplasm. On electron microscopic radioautograms of whole mount cultured cells, silver grains were localized not on the peroxisome but on the cytoplasmic matrix specially over the endoplasmic reticulum. From these results, it is concluded that bezafibrate was localized over endoplasmic reticulum. This fact suggests that the receptor of the peroxisome proliferator should be associated with the endoplasmic reticulum or that the receptor exists on the endoplasmic reticulum. Thus, it is demonstrated that the peroxisome proliferator acts on the endoplasmic reticulum of hepatocytes to proliferate peroxisomes.