LC-MSMS based screening of emerging pollutant degradation by different peroxidases

Abstract

BackgroundThe presence of a wide range of bioactive organic pollutants in wastewater and municipal water sources is raising concerns about their potential effects on humans. Not surprisingly, various approaches are being explored that can efficiently degrade these persistent organic pollutants. Use of peroxidases has recently been recognized as a novel remediation approach that may have potential advantages over conventional degradation techniques. However, testing the abilities of different peroxidases to degrade diverse emerging pollutants is tedious and cumbersome.ResultsIn the present study, we present a rapid and robust approach to easily test the degradability of 21 different emerging pollutants by five different peroxidases (soybean peroxidase, chloroperoxidase, lactoperoxidase, manganese peroxidase, and horseradish peroxidase) using an LC-MSMS approach. Furthermore, this approach was also used to examine the role of a redox mediator in these enzymatic degradation assays. Our results show that some of the organic pollutants can be easily degraded by all five of the peroxidases tested, whereas others are only degraded by a specific peroxidase (or when a redox mediator was present) and there are some that are completely resistant to degradation by any of the peroxidases tested (even in the presence of a redox mediator). The degradation of furosemide and trimethoprim by soybean peroxidase and chloroperoxidase, respectively, was investigated in detail by examining the transformation products generated during their degradation. Some of the products generated during enzymatic breakdown of these pollutants have been previously reported by others, however, we report many new transformation products.ConclusionsLC-MSMS approaches, like the one described here, can be used to rapidly evaluate the potential of different peroxidases (and redox requirements) to be used as bioremediation agents. Our preliminary result shows peroxidases hold tremendous potential for being used in a final wastewater treatment step.

Efficient Degradation of 2-Mercaptobenzothiazole and Other Emerging Pollutants by Recombinant Bacterial Dye-Decolorizing Peroxidases

“…It is worth highlighting the interesting obervation that roxithromycin, the highest molecular weight (836 g/mol) EP tested in our study, which was completely recalcitrant to all the rDyPs tested, showed around 50% degradation with Pf DyP in the presence of HOBT ( Table 3 ). However, as seen in our current study, the addition of a redox mediating species is not universally beneficial [ 36 ] and some redox mediating species exert no influence on the catalytic efficiency of the enzymes [ 36 , 42 , 43 ]. For example, the degradation of all pollutants by Tc DyP was unaffected when HOBT was added to the system ( Table S1 ).…”

“…We have recently published on the potential use of a bioanalytical approach that can be used to simultaneously test the peroxidase-mediated degradation of a large number of organic pollutants in a mixture. The study has described the use of LCMSMS to develop an MRM method that can simultaneously detect 21 different EPs in solution [ 36 ]. A similar MRM approach was adopted in this study, which was based on using LCMSMS to develop an MRM method for 31 EPs belonging to different chemical classes.…”

“…For example, the degradation of all pollutants by Tc DyP was unaffected when HOBT was added to the system ( Table S1 ). Additionally, it has been reported that, in some cases, the addition of redox mediators to an enzymatic system might, in fact, decrease the catalytic efficiency of the degradation due to competition for the active site between the redox mediator and organic pollutants [ 36 ]. Indeed, in the current study, the remediation of a few EPs by rDyPs was inhibited in the presence of HOBT ( Table S1 ).…”

“…LCMSMS was used to quantify the 31 EPs before and after the DyP-mediated degradation. A sensitive and selective method based on a previously published study [ 36 ] was used, where the LCMSMS (Agilent 6420 Triple Quadrupole Mass Spectrometer (Agilent technologies, Santa Clara, CA, USA) was used in the multiple reaction monitoring (MRM) mode to simultaneously detect and quantify 31 EPs in a mixture. The MRM mode is capable of simultaneously detecting “precursor-to-product” ion transitions of an individual compound after being fragmented into specific fragments.…”

“…A dual-polarity electrospray ionization (ESI) source was used to ionize the eluted compounds in both positive and negative polarity modes. The mass spectrometry operating parameters for capillary voltage, nebulizer pressure, temperature of the gas and gas flow rate were set to 4000 V, 45 psi, 8 L/min, and 325 °C, respectively, as previously reported [ 36 ].…”