Identification of Potentially Toxic Transformation Products Produced in Polycyclic Aromatic Hydrocarbon Bioremediation Using Suspect and Non-Target Screening Approaches

Polycyclic
aromatic hydrocarbons (PAHs) are a class of ubiquitous
environmental contaminants that can be remediated through physical,
chemical, or biological means. Treatment strategies can lead to the
formation of PAH-transformation products (PAH-TPs) that, despite having
the potential for adverse ecological and human health effects, are
unregulated and understudied in environmental monitoring and remediation.
Unavailability of reference standards for PAH-TPs limits the ability
to identify PAH-TPs by targeted methods. This study utilized suspect
and nontarget screening approaches to identify PAH-TPs produced by
a bacterial culture, Rhodococcus rhodochrous ATCC 21198, using liquid chromatography-high resolution mass spectrometry.
Open-source tools were used to predict biotransformation products,
predict potential PAH-TP structures from mass spectra, and estimate
health hazards of potential PAH-TPs. The workflow developed in this
study allowed for the tentative identification of 16 PAH-TPs (confidence
levels 2a to 3), seven of which were not previously detected by targeted
analysis. Several new potential transformation pathways for our bacterial
pure culture were suggested by the PAH-TPs, including carboxylation,
sulfonation and up to three hydroxylation reactions. A computational
toxicity assessment indicated that the PAH-TPs shared many hazard
characteristics with their parent compounds, including genotoxicity
and endocrine disruption, highlighting the importance of considering
PAH-TPs in future PAH studies.