Identification of Enantiomeric Byproducts During Microalgae-Mediated Transformation of Metoprolol by MS/MS Spectrum Based Networking.

Yang Wu,Min Lv,Yan Li,Yin-Ru Chiang,Qian Sun,Lingxin Chen,Chang-Ping Yu,Yuwen Wang,Ching Lo,Cheng-Chih Hsu

doi:10.3389/fmicb.2018.02115

Abstract

Metoprolol (MPL) is a chiral β-blocker ubiquitously detected in various environments due to its low to moderate removal in wastewater treatment plants. This study was conducted to test the potential of using microalgae to degrade emerging contaminant MPL and to characterize the enantiomeric enrichment during MPL degradation by microalgae. The results showed that PO43−- P, NO3−- N and MPL could be simultaneously removed in the synthetic effluent by the targeted microalgae species, indicating microalgae were promising in wastewater treatment. Stereoselectivity was observed during MPL degradation by microalgae, with R-form enrichment. A marginal linear relationship between MPL degradation and enantiomeric enrichment was observed, implying that the enantiomeric tool, used as a quantitative indicator of biodegradation, could possibly be applied in MPL degradation by microalgae. An efficient liquid chromatograph tandem high resolution mass spectrometry (LC-HRMS/MS) chiral analytical method was developed to identify transformation products (TPs). The results showed that MS/MS spectral similarity networking could be used as a powerful tool to quickly identify unknown TPs. A total of 6 pairs of chiral TPs were identified, among which two new TPs of MPL including hydroxy{4-[2-hydroxy-3-(isopropylamino)propoxy]phenyl}acetic acid (α-HMPLA) and 4-[2-Hydroxy-3-(isopropylamino)propoxy]benzaldehyde (DMPLD) were firstly reported, and proposed transformation pathways of MPL by microalgae were given. Considering the paired TPs detected and that the degradation of the two enantiomers followed first order kinetics, the two enantiomers likely had the same degradation mechanism.

Highlights

The occurrence of pharmaceuticals in the wastewater is an issue of great concern, because current wastewater treatment processes can not effectively remove them (Sun et al, 2014; Ashfaq et al, 2017; Ben et al, 2018)
The microalgae growth was observed with the microalgae numbers increase by 1.4 fold and 4.4 fold for Haematococcus pluvialis and Scenedesmus quadricauda, respectively, which was in consistent with the higher removal of PO43−- P by Scenedesmus quadricauda
1http://gnps.ucsd.edu control (P > 0.05), indicating that MPL removal was likely attributed to biodegradation

Summary

Introduction

The occurrence of pharmaceuticals in the wastewater is an issue of great concern, because current wastewater treatment processes can not effectively remove them (Sun et al, 2014; Ashfaq et al, 2017; Ben et al, 2018). With the increasing concern of the potential risks which pharmaceuticals could pose to ecology and human health, enhanced removals of pharmaceuticals in wastewater treatment systems are increasingly needed. Microalgae have been suggested to be promising in wastewater treatment, since it could efficiently “recycle” nitrogen (N) and phosphorus (P) from treated effluents (Menger-Krug et al, 2012; Cai et al, 2013; Van Wagenen et al, 2015). There is a great potential of applying microalgae in treated effluent wastewater. Considering limited microalgae species and pharmaceuticals have been tested, there is a need to examine more algae-mediated removal of pharmaceuticals and to elucidate pathways for algaemediated pharmaceutical transformation

Objectives

Methods

Results