Urase laboratory web site

Biological Degradation of Xenobiotics

Separate estimation of adsorption and degradation of pharmaceutical substances and estrogens in the activated sludge process

ABSTRACT; Taro Urase, and Tomoya Kikuta. Water Research, 39, 1289-1300, 2005.

The removal of three estrogens such as 17beta-estradiol, two endocrine disruptors like bisphenol A, and ten pharmaceutical substances like ibuprofen (IBP) by the activated sludge was experimentally examined. The contribution of adsorption and degradation to the overall removal was estimated separately and successfully. At the neutral pH condition, the target pharmaceutical substances showed little tendency of adsorption to the sludge and their water-sludge partition coefficients were lower than those of the target estrogens. On the other hand, the increasing tendency of adsorption was observed in the lower pH condition. A linear relationship between the log of the partitioning coefficient and the log Kow was observed when pH was lowered to keep the pharmaceuticals neutral solutes. The acidic operational condition was preferable for the removal of acidic pharmaceutical substances because the limiting stage for the removal was not biodegradation but the transfer of the substances from the water phase to the sludge phase.

Keywords; Reaction kinetics, pharmaceutical substances, endocrine disruptors, estrogens, adsorption, activated sludge

The characteristics of enriched nitrifier culture in the degradation of selected pharmaceutically active compounds

ABSTRACT; Ngoc Han Tran, Taro Urase, Osamu Kusakabe. J. of Hazardous Materials, 171, 1051-1057, 2009.

The biodegradation of 10 selected pharmaceuticals by enriched nitrifier cultures with ammonia oxidizing activity of 30 mg NH4-N/g MLVSS h was investigated under various initial operating conditions such as in the presence of different growth substrates and inhibitors. The enriched nitrifier culture showed 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 in the ammonium concentration. A higher removal efficiency of CA, DCF, CBZ and PPZ was obtained when organic substrates were added. The contribution of autotrophs and heterotrophs 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 with and without ATU addition 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.

Keywords; Activated sludge, Degradation, Enriched nitrifier culture, Pharmaceuticals

Biodegradation characteristics of selected pharmaceutical substances by whole fungal culture Trametes versicolor and its laccase

ABSTRACT; Ngoc Han Tran, Taro Urase, Osamu Kusakabe. Journal of Water and Environment Technology, 8, 2, 125-140, 2010.

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 (2,2f-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.

Keywords; Degradation, white-rot fungal laccase, pharmaceutically active compounds (PhACs)

Aerobic and Anaerobic Biological Degradation of Pharmaceutically Active Compounds in Rice Paddy Soils

ABSTRACT; Pahaerdin Nazhakaiti, Hirofumi Tsutsui and Taro Urase, Applied Sciences. 9(12), 2505, 2019.

One of the concerns against the use of sewage sludge for agricultural purposes is emerging contaminants contained in sewage sludge. Most of the studies on biological degradation of pharmaceutically active compounds in agricultural land were carried out with water-unsaturated soils under relatively aerobic conditions. In this study, the degradation of pharmaceuticals mainly including non-steroidal anti-inflammatory drugs (NSAIDs) was investigated in Asian rice paddy soils that are flooded in anaerobic condition. The experimental results showed that the concentrations of the target pharmaceuticals excluding the exception of naproxen were poorly decreased in anaerobic condition. On the other hand, the microbial communities of the soils contained the aerobic degraders of clofibric acid and diclofenac, which are generally persistent in biological wastewater treatment. The higher degradation rates in aerobic condition suggest the possibility of enhanced degradation of pharmaceuticals by supplying oxygen with plowing anaerobic rice fields or with drying the field in off-season for farming.

Keywords; paddy soil, pharmaceutically active compounds, sewage sludge, wastewater treatment

 

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