Microbial-Fet Alcohol Sensor

Abstract

A microbial-FET alcohol sensor was developed using immobilized acetic acid bacteria, a gas permeable membrane and an Ion Sensitive Field Effect Transistor (ISFET). The acetic acid bacteria were immobilized on the gate of the ISFET in calcium alginate gel. Both ISFET-immobilized microorganisms and Ag/AgCl reference electrode were set into a small shell which was filled with inner buffer (5 mM tris-HC1 buffer containing 0.1 M CaC1₂, pH 7.0). The side wall of the shell was equipped with a gas permeable membrane to allow the passage of alcohol into the inner buffer. The alcohol sensor responded to 0.1 mM ethanol and a linear relationship was obtained between the initial rate of response (dV_g/dt) and the logarithmic ethanol concentration in the range between 3 – 70 mM. The alcohol sensor specifically responded to ethanol, 1-propanol and 1-butanol but did not respond to methanol, secondary alcohols and other nutrients (sugars and organic acids). The alcohol sensor was stable at pH 2 – 12 and at 15 – 25°C for 15 hours.