EVALUATION OF A GLUCONOBACTER-OXYDANS WHOLE-CELL BIOSENSOR FOR AMPEROMETRIC DETECTION OF XYLOSE

Whole cells of Gluconobacter oxydans were employed in a microbial sens or for xylose determinations using Clark-type electrodes. Bacterial ce lls were immobilized on chromatographic paper by simple physical adsor ption and attached to the surface of the electrodes. The lower limit o f xylose detection was approximately 0.5 mM and measurements were usef ul up to at least 20 mM xylose. Physiological buffers showed little ef fect on biosensor function. Responses were highly reproducible, showin g a standard deviation of 67% over 10 consecutive measurements. Whole cell biosensors were relatively stable, retaining 60% of initial activ ity after 35 days of dry storage at 4 degrees C. Xylose detection was not significantly affected by the presence of xylitol, suggesting that biosensors will be useful in monitoring conversions of these compound s. However, glucose or ethanol elicited a 10-fold higher response than xylose at equal concentrations (1 mM). Such interfering materials wil l need to be controlled or concurrently monitored in specific sensor a pplications. (C) 1997 Elsevier Science Limited.