Taro Urase's Laboratory

Abstract of Doctral Dissertation

Enhanced biodegradation of pharmaceutically active compounds using enriched nitrifier culture, white-rot fungal culture, and commercial laccase

Tran Ngoc Han

The biodegradation of ten selected pharmaceuticals by enriched nitrifier cultures with ammonia oxidizing activity of 30 mg NH4-N/gMLVSS.h was investigated under various initial operating conditions such as in the presence of different growth substrates and inhibitors. The enriched nitrifier culture showed the higher degradation of the target pharmaceuticals than the conventional activated sludge. The degradation efficiency of persistent pharmaceuticals such as clofibric acid (CA), diclofenac (DCF), carbamazepine (CBZ) and propyphenazone (PPZ) was increased with the increase of the ammonium concentration. A higher removal efficiency of CA, DCF, CBZ and PPZ was obtained when organic substrates added. The contribution of autotrophs and hetrotrophs in the biotransformation of the pharmaceuticals by the enriched nitrifier culture was successfully estimated by the addition of inhibitors. Experimental results showed that the high degradation of IBP and partial degradation of other selected pharmaceuticals were observed in the presence of allylthiourea (ATU), an ammonia monooxygenase inhibitor, reflecting the activity of heterotrophic bacteria, while the results without ATU showed that the contribution of the nitrification in the degradation of most pharmaceuticals was also dominant. The results suggest that nitrification can enhance the biotransformation of pharmaceutical substances.

The degradation of 10 selected pharmaceuticals by whole fungal culture Trametes versicolor, culture filtrates and commercial laccase preparation was conducted. Complete removal of diclofenac (DCF), naproxen (NPX), indomethacin (IDM), ibuprofen (IBP), and fenoprofen (FEP) and partial degradation of other selected PhACs were observed after 48 hours of incubation with the 7-day-old liquid fungal culture in the cases of both the presence and the absence of ABTS (2,2f-azino-bis(3-ethyl-benzothiazoline-6-sulfonic acid)) as a laccase-mediator. The catalytic activity of laccase in the degradation of selected PhACs was examined for cases of both crude and commercial extracellular laccase preparations. The results showed that laccase preferentially removed DCF, NPX and IDM among the target PhACs removed by the whole fungal culture. Intracellular enzymes may degrade other compounds. The removal of most selected PhACs was increased with the increase in laccase activity. The presence of redox mediators such as ABTS and HBT (1-hyroxybenzotriazole) promoted the degradation of selected PhACs, in which complete degradation of DCF, NPX and IDM was observed after 3 hours of incubation with laccase activity (2000 U/l) in the presence of ABTS/HBT. The degradation spectrum by laccase for ionic pharmaceuticals with nitrogen containing structure was quite different from that of the activated sludge process.