Comparison of microbial sensors based on amperometric and potentiometric electrodes

Abstract

Microbial sensors based on oxygenn and carbon dioxide electrodes coupled with immobilized Saccharomyces are compared for measurements of glucose and other carbohydrates. With the oxygen sensor, the yeast works under aerobic conditions but anaerobically with the carbon dioxide sensor. The two metabolisms of the same strain make little difference to the lifetimes (> 15 days), selectivities and response rates (5–10 min) of the sensors. The effects of pH are very different owing to the pH sensitivity of the carbon dioxide sensor. The viable concentration ranges overlap; the oxygen-based sensor is more useful for low concentrations of glucose (0.01–1 mmol l −1) while the carbon dioxide-based sensor is better suited for 1–10 mmol l −1. With the oxygen-based sensor, the response time is governed by the rate of metabolism; with the carbon dioxide-based sensor, the response time of the potentiometric carbon dioxide electrode is the rate determining step.