Ammonia sensor with flavin-containing monooxygenase

摘要

A biosensor for ammonia solution was developed with a flavin-containing monooxygenase-3 (FMO3). The biosensor consisted of a Clark-type dissolved oxygen electrode and an FMO3 immobilized membrane. In order to amplify the biosensor output, a substrate regeneration cycle obtained by coupling the monooxygenase with L-ascorbic acid (AsA) as the reducing reagent system, was applied. The AsA 10.0mmolL~(-1) concentration was able to optimally amplify the sensor output 11 times greater. The FMO3 biosensor was used with AsA to measure ammonia solution from 3.20 to 14.29 mmol L~(-1) and from 0.09 to 21.7mmolL~(-1) with 5.0 and 10.0mmol L~(-1) AsA, respectively. The FMO biosensor also had a good reproducibility such as a 2.5% coefficient of variation in eight multiple measurements, and the output current was maintained over a few hours. The selectivity of the FMO biosensor being attributed to enzyme specificity was obtained for several chemical substances (trimethyl amine, methyl mercaptan, dimethyl sulphide, and so on).