title: A rapid and simple respirometric biosensor with immobilized cells of Nitrosomonas europaea for detecting inhibitors of ammonia oxidation.
abstract: As obligate chemolithotrophs, ammonia-oxidizing bacteria (AOB) grow very slowly and are known to be extremely sensitive to a wide variety of inhibitors. Since it is generally accepted that inhibition of ammonia oxidation by AOB results in a total failure of nitrogen removal, it is necessary to develop a method to detect inhibitors of ammonia oxidation in wastewater. Since ammonia oxidation accompanies oxygen consumption, ammonia oxidation can be easily evaluated by measuring oxygen consumption rate using a dissolved oxygen (DO) probe. In this study, a rapid and simple respirometric biosensor using the pure culture of Nitrosomonas europaea was developed. N. europaea was cultivated in a continuous fermentor operating at the dilution rate of 0.008 h(-1) to obtain physiologically constant cells and was immobilized onto the dialysis membrane through filtration. DO, determined by the biosensor, started to increase 30 s later after ammonia oxidation inhibitor was fed, and a new steady-state DO was obtained in 10-30 min. For this DO profile, steady-state kinetics was applied to evaluate ammonia oxidation efficiency. The concentration of a toxic compound causing 50% decrease of oxygen-consumption activity (EC50) was determined for different chemicals. The EC50 values obtained with the biosensor (0.018 mg l(-1) for allylthiourea, 0.027 mg l(-1) for thioacetamide, 1.10 mg l(-1) for phenol and 0.0 1mg l(-1) for thiourea) indicated that the developed biosensor was highly sensitive to a variety of the inhibitors. It was also shown that the biosensor is applicable for on-line real time monitoring.
authors.affiliation: Department of Environmental Engineering and Biotechnology, Myongji University, San 38-2, Namdong, Yongin, Kyonggido 449-728, Republic of Korea.
authors.forename: Rong
authors.initials: R
authors.lastname: Cui
authors.forename: Wook-Jin
authors.initials: WJ
authors.lastname: Chung
authors.forename: Deokjin
authors.initials: D
authors.lastname: Jahng
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D001681:Biological Assay / Q000295:instrumentation / Q000379:methods; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D018914:Cells, Immobilized / Q000187:drug effects / Q000502:physiology; D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D043370:Nitrosomonas europaea / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D010084:Oxidation-Reduction / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology*; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000494:pharmacology*
chemical_list: D014874:Water Pollutants, Chemical; D000641:Ammonia