Biodegradation of Microtoxic Phenylpropanoids (Phenylpropanoic Acid and Ibuprofen) by Bacteria and the Relevance for Their Removal from Wastewater Treatment Plants.

The NSAID ibuprofen (2-(4-isobutylphenyl)propanoic acid) and the structurally related 3-phenylpropanoic acid (3PPA), are widely used pharmaceutical and personal care products (PPCPs) which enter municipal waste streams but whose relatively low rates of elimination by wastewater treatment plants (WWTPs) are leading to the contamination of aquatic resources. Here, we report the isolation of three bacterial strains from a municipal WWTP, which as a consortium are capable of mineralizing ibuprofen. These were identified as the species, termed RW422, RW423 and RW424, in which the first two of these isolates were shown to contain the catabolic operon responsible for the first steps of ibuprofen mineralization. These genes which are associated with plasmids could, experimentally, only be transferred between other species, such as from the ibuprofen degrading RW412 to the dioxins degrading RW1, generating RW421, whilst a transfer from the isolates to RW1 was not observed. RW412 and its derivative, RW421, as well as the two-species consortium RW422/RW424, can also mineralize 3PPA. We show that IpfF can convert 3PPA to 3PPA-CoA; however, the growth of RW412 with 3PPA produces a major intermediate that was identified by NMR to be cinnamic acid. This and the identification of other minor products from 3PPA allows us to propose the major pathway used by RW412 to mineralize 3PPA. Altogether, the findings in this study highlight the importance of genes, horizontal gene transfer, and alternative catabolic pathways in the bacterial populations of WWTPs to eliminate ibuprofen and 3PPA.