FET-MICROBIAL SENSOR FOR XYLOSE DETECTION BASED ON GLUCONOBACTER-OXYDANS CELLS

A potentiometric biosensor for xylose was devised utilizing Gluconobac ter oxydans whole cells. Immobilization methods based on physical adso rption were used for G. oxydans cells and extracellular pH changes res ulting from xylose dehydrogenation were monitored by a field effect tr ansistor (FET). The G. oxydans, FET-based sensor detected xylose at a lower limit of 0.5 mM. From 5.0 to 30 mM xylose, the response of the s ensor was linear. Expectedly, output signals were significantly suppre ssed by buffer (Tris-HCl). Responses were essentially stable for at le ast four weeks of storage and showed only a slight loss of initial xyl ose sensitivity. Xylitol exerted an insignificant influence on the sen sor's response to xylose. However, the response to glucose was 5 times higher in relation to that of xylose at the same concentration (1 mM) . For xylose determinations in the presence of glucose, a two-step ass ay is discussed.