No abstract

Carbamazepine (CBZ) is a pharmaceutical frequently categorized as a recalcitrant pollutant in the aquatic environment. Endophytic bacteria previously isolated from reed plants have shown the ability to promote growth of their host and to contribute to CBZ metabolism. In this work, a horseradish (Armoracia rusticana) hairy root (HR) culture has been used as a plant model to study the interactions between roots and endophytic bacteria in response to CBZ exposure. HRs could remove up to 5% of the initial CBZ concentration when they were grown in spiked Murashige and Skoog (MS) medium. Higher removal rates were observed when HRs were inoculated with the endophytic bacteria Rhizobium radiobacter (21%) and Diaphorobacter nitroreducens (10%). Transformation products resulting from CBZ degradation were identified using liquid chromatography-ultra high-resolution quadrupole time of flight mass spectrometry (LC-UHR-QTOF-MS). CBZ metabolism could be divided in four pathways. Metabolites involving GSH conjugation and 2,3-dihydroxylation, as well as acridine related compounds are described in plants for the first time. This study presents strong evidence that xenobiotic metabolism and degradation pathways in plants can be modulated by the interaction with their endophytic community. Hence it points to plausible applications for the elimination of recalcitrant compounds such as CBZ from wastewater in CWs.

No abstract

Based on the known ability of the white rot fungus Phanerochaete chrysosporium to metabolize PAHs, a fungal reactor system with separate soil extraction and fungal incubation units was constructed. The design of the system allowed samples to be easily removed at strategic positions and to ascertain mineralization. The highly contaminated soil (1−2 mm particle diameter), with a total EPA Method 610 concentration of 41 g of PAHs kg-1, was spiked with [7,10-14C]benzo[a]pyrene in order to follow the fate of this tracer by HPLC and high-performance gel permeation chro matography. While mineralization amounted to only 2.5%, it was observed that the fungus reduced the total soil PAH concentration by 45% through polymerization processes. For [7,10-14C]benzo[a]pyrene, a value of 4.9 mg kg-1 day-1 or overall 5.5% was obtained. The polymers remained as sociated with soil, and no monomeric PAHs were detected in the medium. In parallel experiments without soil, high molecular weight polymers could be found in the medium. Sterile soil and medium controls revealed no polymerization. The results were consistent with literature reports that P. chrysosporium converts PAHs primarily to quinones, which have a strong tendency to polymerize. On the basis of the success of this system, scaling up appears to be justifiable.