Abstract
SUMMARYResearch backgroundThe occurrence and environmental toxicity of pharmaceuticals have recently attracted increasing attention. Diclofenac is a highly consumed non-steroidal anti-inflammatory drug, which is often detected in wastewaters, but investigations of its influence on bacteria are scarce.Experimental approachWe investigated the influence of this pharmaceutical on bacterial community in activated sludge exposed to increasing concentrations of diclofenac in fed-batch reactors over 41 days. Nitrification activity of the activated sludge was measured and changes in bacterial community structure were followed using culture-independent molecular method (terminal restriction fragment length polymorphism, T-RFLP) and by the cultivation approach.Results and conclusionsNitrification activity was not detectably influenced by the addition of diclofenac, while the main change of the bacterial community structure was detected only at the end of incubation (after 41 days) when diclofenac was added to artificial wastewater as the only carbon source. Changes in community composition due to enrichment were observed using cultivation approach. However, taxonomic affiliation of isolates did not match taxons identified by T-RFLP community profiling. Isolates obtained from activated sludge used as inoculum belonged to five genera: Comamonas, Arthrobacter, Acinetobacter, Citrobacter and Aeromonas, known for their potential to degrade aromatic compounds. However, only Pseudomonas species were isolated after the last enrichment step on minimal agar plates with diclofenac added as the sole carbon source.Novelty and scientific contributionOur results suggest that the selected recalcitrant and commonly detected pharmaceutical does not strongly influence the sensitive and important nitrification process of wastewater treatment. Moreover, the isolated strains obtained after enrichment procedure that were able to grow on minimal agar plates with diclofenac added as the only carbon source could serve as potential model bacteria to study bacterial diclofenac degradation.
Highlights
Pharmaceuticals, generally regarded as being extremely advantageous for increasing human life expectancy, on the other hand represent a serious burden for the environment
Only Pseudomonas species were isolated after the last enrichment step on minimal agar plates with diclofenac added as the sole carbon source
The isolated strains obtained after enrichment procedure that were able to grow on minimal agar plates with diclofenac added as the only carbon source could serve as potential model bacteria to study bacterial diclofenac degradation
Summary
Pharmaceuticals, generally regarded as being extremely advantageous for increasing human life expectancy, on the other hand represent a serious burden for the environment. Worldwide consumption rates of hundreds of tonnes of pharmaceuticals have a potential to cause undesirable ecological and human health effects [1,2,3]. The pharmaceutical industry has increased enormously in recent years and currently represents one of the most profitable branches of industry. Substantial amounts of pharmaceuticals can reach and impact the environment, either through direct discharge of pharmaceuticals or due to inefficient elimination in wastewater treatment plants (WWTPs). Several studies have demonstrated that some pharmaceuticals are efficiently eliminated by WWTPs (ibuprofen, naproxen, ketoprofen), while others are resistant to biodegradation (diclofenac, clofibric acid) [4,5,6,7].
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