Concern over the exposure to active pharmaceutical compounds (PCs) in the environment is increasing. Many PCs are not fully removed during municipal wastewater treatment, thus they are released to the environment with the treated effluents. Consequently, PCs and their potentially toxic degradation products may be found in surface and groundwater and being introduced into agricultural soils, where they can accumulate and be taken up by crops. Carbamazepine (CBZ) is a widely used anticonvulsant drug which serves as a model compound in the study of environmental exposure and removal of PCs. This study aims to elucidate CBZ removal pathway by the white rot fungus Pleurotus ostreatus from both biological and chemical point of view.
When P. ostreatus was grown in glucose peptone medium 99% of the added CBZ were transformed to the active metabolite EP-CBZ, by cytochrome P450 and manganese peroxidase. When P. ostreatus was grown on cotton stalks, 90% of the added CBZ have been removed, and novel degradation pathways were discovered. Some of the new degradation products (acridine, acridone and 1-(2-benzaldehyde)-(1H,3H)-quinazoline-2,4-one (BQD) are known to be toxic. The formation of these additional products during growth on cotton stalks comparing to GP medium can be due to activity of different enzymatic systems, or as a result of an oxidative environment rich of free radicals that is formed during lignin degradation.
This work highlights the effect of growth conditions on the degradation pathway of PCs and formation of possibly toxic degradation products. This is of importance in the context of release of PCs to the environment, e.g. irrigation with treated wastewater.
