Browsing by Author "Udundzic, Anja"
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- Searching for bacteria degrading carbamazepine, diclofenac sodium, and 17a-ethinylestradiol from sewage sludge digestor sample and in silico identification of genes potentially involved in the biodegradation of these drugsPublication . Udundzic, Anja; Costa, Maria Clara Semedo da Silva; Carlier, Jorge Daniel DiasThe steady global increase of various contaminants of concern (CEC), including pharmaceuticals, has raised serious concerns about their residues potentially posing an environmental threat, particularly in water. While wastewater treatment plants (WWTPs) should manage and control these contaminants, conventional treatment methods often fail to adequately eliminate the persistent toxic compounds, emphasizing the need for improving managing approaches. Bioaugmentation, involving the introduction of specific microorganisms, has immense potential for enhancing wastewater treatment by facilitating the biological breakdown of toxins into less harmful substances. The objective of this study was to search for bacterial strains in a sewage sludge digestor sample that are competent in biodegrading three commonly found pharmaceutical compounds in wastewater effluents; carbamazepine (CBZ), diclofenac sodium (DCS), and 17α-ethinylestradiol (EE2), along with in silico identification of genes potentially involved in their biodegradation. Initially, tests with different mobile phases were performed to refine the HPLC methods used to quantify the targeted pharmaceuticals and calibration curves were made for each method. Following, biosorption assays determined the affinity of the pharmaceuticals to an inactivated sewage sludge digestor sample, where the highest affinity was detected in EE2, binding 64%, while the CBZ and DCS were bound by just over 10% each. Successive enrichment cultures starting from active sludge in selective liquid media (with CBZ, DCS, or EE2 as the sole carbon source) were prepared and used to inoculate plates of selective solid media. Thirty-seven (37) strains were isolated, grown, and subsequently tested as pure cultures in liquid media, where the biodegradation assays showed low or no degradative capabilities. Strain CBZ 3.5.2, causing a 30% CBZ removal, was classified based on the 16S rRNA gene sequence as Achromobacter pulmonis, or Bordetella hinzii, and used for further tests with replicates. However, the confirmation tests failed to replicate the decrease in the CBZ concentration. Ultimately, in silico searches in the genomes of species for which there are reports of strains degrading CBZ and DCS were performed to identify genes likely associated with biodegradation of the targeted pharmaceuticals. This search generated a significant volume of results, highlighting opportunities for further investigation.