High-Throughput Identification of Microbial Transformation Products of Organic Micropollutants

Abstract

During wastewater treatment, many organic micropollutants undergo microbially mediated reactions resulting in the formation of transformation products (TPs). Little is known on the reaction pathways that govern these transformations or on the occurrence of microbial TPs in surface waters. Large sets of biotransformation data for organic micropollutants would be useful for assessing the exposure potential of these TPs and for enabling the development of structure-based biotransformation prediction tools. The objective of this work was to develop an efficient procedure to allow for high-throughput elucidation of TP structures for a broad and diverse set of xenobiotics undergoing microbially mediated transformation reactions. Six pharmaceuticals and six pesticides were spiked individually into batch reactors seeded with activated sludge. Samples from the reactors were separated with HPLC and analyzed by linear ion trap-orbitrap mass spectrometry. Candidate TPs were preliminarily identified with an innovative post-acquisition data processing method based on target and non-target screenings of the full-scan MS data. Structures were proposed following interpretation of MS spectra and MS/MS fragments. Previously unreported microbial TPs were identified for the pharmaceuticals bezafibrate, diazepam, levetiracetam, oseltamivir, and valsartan. A variety of previously reported and unreported TPs were identified for the pesticides. The results showed that the complementary use of the target and non-target screening methods allowed for a more comprehensive interpretation of the TPs generated than either would have provided individually.

Environmental Fate and Toxicology of Clomazone

“…Biotransformation of clomazone was studied by Helbling et al (2010). Sludge collected from a pilot-scale wastewater treatment plant was spiked with pesticides and pharmaceuticals;…”

Targeted and non-targeted liquid chromatography-mass spectrometric workflows for identification of transformation products of emerging pollutants in the aquatic environment

“…Molecules with N-, O-, or S-alkyl groups were probably transformed to dealkylated forms, as observed for naproxen [53], triclosan [57], diclofenac [41] and ICM [46,47]. Other oxidative reactions included ring opening, oxidative deamination and oxidative dechlorination [34,45,50,56].…”

“…During such experiments, spiked and non-spiked samples run in parallel, as do spiked autoclaved diluted sludge or autoclaved groundwater and ultrapure water in order to correct for abiotic processes [39]. Samples are collected periodically so that the reaction kinetics of the analytes can be determined sufficiently [33,50].…”

“…Membrane bioreactors (MBRs), air-pulsed fluidized-bed bioreactors and sequencing batch reactors (SBRs) [37,50] are more realistic systems than batch reactors, because they better simulate the conditions in the full-scale system.…”

“…As UM-PPS is freely accessible and all rules applied are clearly assigned, it is the most common prediction tool in suspect screening, and many researchers have tried to evaluate and to improve its prediction power [34,[50][51][52]. The prediction rules behind UM-PPS come from the University of Minnesota Biocatalysis/ Biodegradation Database (UM-BBD) and literature [85].…”