The presence of non-steroidal anti-inflammatory drugs, such as diclofenac (DCF), in the environment, is an emerging problem due to their harmful effects on non-target organisms, even at low concentrations. We studied the biodegradation of DCF by the strain D15 of Enterobacter hormaechei. The strain was isolated from an activated sludge, and identified as E. hormaechei based on its physiological characteristics and its 16 S RNA sequence. Using HPTLC and GC-MS methods, we demonstrated that this strain metabolized DCF at an elimination rate of 52.8%. In the presence of an external carbon source (glucose), the elimination rate increased to approximately 82%. GC-MS analysis detected and identified one metabolite as 1-(2,6-dichlorophenyl)-1,3-dihydro-2H-indol-2-one; it was produced as a consequence of dehydration and lactam formation reactions.

The presence of pharmaceuticals at low concentrations (ng to μg) in the environment has become a hot spot for researchers in the past decades due to the unknown environmental impact and the possible damages they might have to the plantae and fauna present in the aquatic systems, as well as to the other living organisms. The aim of the present investigation was to develop a bacterial consortium isolated from different origins to evaluate the ability of such a consortium to remove a mixture of pharmaceuticals in the batch system at lab scale, as well as assessment of its resistance to the other micropollutants present in the environment. Using a closed bottle test, biodegradation of the mixed pharmaceuticals including Diclofenac (DCF), Ibuprofen (IBU), and Sulfamethoxazole (SMX) (at a concentration of 3 mg.L of each drug) by the bacterial consortium was investigated. The test was carried out under metabolic (pharmaceutical was used as the sole source of carbon) and co-metabolic condition (in the presence of glucose). Finally, the ability of the bacterial consortium to resist other micropollutants like antibiotics and heavy metals was investigated. Under the metabolic condition, the mixed bacteria (i.e., consortium) were able to metabolize 23.08% and 9.12% of IBU, and DCF at a concentration of 3 mg.L of each drug, respectively. Whereas, in co-metabolic conditions, IBU was eliminated totally, in addition, 56% of the total concentration of DCF was removed, as well. In both metabolic and cometabolic conditions, removal of SMX was not observed. The selected bacteria were able to resist to most of the applied antibiotics and the used heavy metals, except mercury, where only one strain (S4) was resistant to the later heavy metal. Results suggest that the developed consortium might be an excellent candidate for the application in the bioremediation process for treating ecosystems contaminated with the pharmaceutical.

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Diclofenac (DCF) belongs to the class of nonsteroidal anti-inflammatory drugs, which is one of the most consumed by population and detected in raw sewage. Several studies have reported variable removal rates by biodegradation of diclofenac in wastewater treatment plants (WWTPs). This study deals with the evaluation of the biodegradation of DCF by a bacterial consortium (obtained from pure cultures of Enterobacter hormaechei D15 and Enterobacter cloacea D16), which were isolated from household compost and Algerian WWTP, respectively, as sole carbon source and by co-metabolism, using glucose as carbon source. A 98% removal rate of DCF was observed when it is used as the sole carbon source, whilst only 44% of DCF was removed in co-metabolic conditions. Two metabolites were identified using ultra-high-performance liquid chromatography coupled to electrospray injection tandem mass spectrometry analysis (UHPLC-ESI-MS/MS); one of them was identified as 4′hydroxy-DCF, and the second metabolite was suspected to be a nitro derivative of DCF, according to comparison with the literature. Biodegradation of DCF by this bacterial consortium generates relatively safe final by-products.

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