3.2. Response curve of the microbial biosensor
The microbial sensorwas immersed in an oxygen-saturated
buffer solution (pH 7, t = 25 ◦C) for equilibration for about
5 min. After a steady-state signal was obtained, ethanol solutions were added in order to obtain final concentrations
in the range 0.05–5 mM. Decrease of the oxygen concentration
around the biocatalytic membrane, due to ethanol
assimilation, was registered, and the potential was stabilised
in 5–7 min depending on the ethanol concentration.
This response time is longer than for the amperometric
biosensor [34] due to the longer response time of the potentiometric
oxygen electrode [24] and due to the presence
of the second gas-permeable membrane between the sample
and the yeast cell layer.
Kinetic measurements could be made in the first 2 min.