| "We have developed biosensors using nitrifying bacteria in order to detect toxicants in purified water, river water arid wastewater. Generally, the toxicants sensitivity of biosensors, which are continuously monitoring the respiration rate of bacteria, is inversely related to the activity of bacteria in biosensors, therefore it has been needed to resolve the variation of the sensitivity because of the activity change of bacteria while biosensors are operating. In this paper, we defined the oxygen consumption ratio (OCR) as the relative activity index of bacteria in biosensors and researched correlation between the sensitivity and parameters of OCR. We found that the operating temperature was the most effective parameter to increase the sensitivity and control OCR. In results we could increase the sensitivity by five fold compared with the objective specification and reduce the variation of the sensitivity during three months operation. We also defined the dependence of OCR on substrate concentration as the relative activity index of bacteria in biosensors; therefore we became to be able to evaluate correctly the sensitivity of biosensors on different conditions." |
