Identification of bacteria from wastewater for the oxidation of micropollutants
The term "micropollutants" includes xenobiotic compounds of various origins which can be found in aquatic environments at concentration levels of nano- to micrograms per liter and which present a negative effect on ecosystems. Many aromatic micropollutants present in municipal wastewater are due to human activities, such as pharmaceuticals or biocides, and are not easily removed by conventional biological treatments in wastewater treatment plants (WWTPs). Fungal laccases and other multicopper oxidases are known to efficiently oxidize a wide spectrum of aromatic compounds, while a few in vitro studies on bacterial enzymes have also suggested the potential to use bacterial oxidases to increase the removal efficiency of micropollutants in WWTPs. In the present study, we chose to focus on the oxidative activities displayed by bacteria present in WWTPs. One aim of this work was to develop a screening method to isolate microorganisms producing oxidases with a potential activity on aromatic micropollutants. The microorganisms were selected on solid rich medium for their ability to oxidize 2,6-dimethoxyphenol (DMP), a chromogenic compound which becomes brown upon oxidation. DMP was chosen among other chromogenic substrates as it was not affecting bacterial growth, is nicely oxidized at neutral pH and is mimicking the basic structure of aromatic micropollutants. Selected bacterial isolates were identified as members of different genera (Pseudomonas, Comamonas, Enterobacter, …) and their ability to oxidize DMP was confirmed in liquid cultures as well as using an in vitro enzymatic assay with crude extracts. Preliminary observations suggested that DMP oxidation is linked with the stationary phase of bacterial growth. Further characterization of the physiology and biochemistry of the oxidases is under investigation for a subset of isolates.
Record created on 2014-06-24, modified on 2016-08-09