Submitted to: Biosensors World Congress
Publication Type: Abstract Only
Publication Acceptance Date: December 4, 1996
Publication Date: N/A
Microbial biosensors were constructed using whole cells of Gluconobacter oxydans immobilized onto pH-sensitive field-effect transistors (FET). Potentiometric responses to glucose, xylose and mixtures of the two were determined. The biosensor had a linear response range of approximately 0.07 to 1.0 mM for glucose, and 5.0 to 100 mM for xylose. A composite curve was obtained experimentally, using mixtures containing glucose at a constant concentration of 0.1 mM and a range of xylose concentrations from 0.1 to 100 mM, and the theoretical response of xylose plus glucose was calculated assuming an additive biosensor response. Experimental values agreed well with theoretical values within the range of 1.0 to 10.0 mM xylose. However, responses deviated greatly from theoretical values in the range of 10 to 100 mM xylose. We suspect that this effect may be caused by differential affinities of enzymes for these substrates. That is, aldose dehydrogenase may lose affinity for glucose in the presence of high concentrations of xylose. Results suggest that it should be possible to employ pattern recognition analysis in conjunction with appropriate dilutions and/or a second sensor to simultaneously measure glucose and xylose within a limited range. Determination of the useful additive and linear ranges will simplify the calibration of biosensors for this application.