Transformation of ibuprofen by Bacillus megaterium – Reversible glycosylation of the unhydroxylated drug and generation of hydroxylated and conjugated metabolites

Several pharmaceuticals persist in wastewater plants and contaminate increasingly natural water bodies, even ground water. In this study, different bacteria with known capabilities to degrade aromatic environmental pollutants – belonging to the genera Bacillus, Paenibacillus, Mycobacterium and Cupriavidus - were screened for their ability to transform the anti-inflammatory drug ibuprofen. Bacillus megaterium SBUG 518 as one of the most efficient strains tested was almost completely inhibited by 0.05% ibuprofen at pH 6 but was able to transform 0.005% ibuprofen within 4 h up to 92%. Four products were identified by HPLC and LC/MS. The drug was transformed via three different biotransformation reactions involving (A) conjugate formation of ibuprofen with a sugar molecule (B) the hydroxylation of the isobutyl side chain at two positions, and (C) glycosylation of 2-hydroxyibuprofen. The ibuprofen conjugate (ibuprofen pyranoside) was considerably less toxic to B. megaterium than the parent compound. Its reversible formation can lead to a temporary remarkable underestimation of ibuprofen concentrations in environmental “elimination” studies. Proteomic analyses including 1264 identified proteins suggest that cytochrome P450 BM3 plays a pivotal role in ibuprofen hydroxylation. Additionally, several proteins involved in stress response as well as proteins with similarity to multidrug efflux pump proteins were found in higher abundance in ibuprofen-incubated bacteria.