A FLUOROMETRIC FIBEROPTIC BIOSENSOR FOR DUAL ANALYSIS OF GLUCOSE AND FRUCTOSE USING GLUCOSE-FRUCTOSE-OXIDOREDUCTASE ISOLATED FROM ZYMOMONAS-MOBILIS

A fluorometric fiber-optic biosensor was used to determine the content of glucose and fructose according to the measurement principle of flow injection analysis (FIA). The enzyme glucose-fructose-oxidoreductase (GFOR) isolated from Zymomonas mobilis was confined in a measurement cell behind an ultrafiltration membrane. The GFOR catalyzes the oxidation of glucose to gluconolactone and the reduction of fructose to sorbitol according to the ping-pong mechanism. This unique enzyme contains NADPH tightly confined in the enzyme complex. The change of NADPH fluorescence was detected by a fluorosensor. The stability could be increased remarkably by crosslinking with glutaraldehyde. The detection range for glucose was within a concentration range of 0.055-55.5 mM and that for fructose within 0.278-331 mM. The response time for glucose and fructose was in the range of 40 s and 1 min, respectively. Steady-state was achieved for glucose injection in 2 min and fructose injection in 6.5 min. Sampling time for glucose could be reduced to 37% by including fructose in excess to the sample. This also makes the regenerating step unnecessary. The specificity of this biosensor was tested for different sugars. The results showed that this biosensor system is highly specific, sensitive and suitable for dual analysis of glucose and fructose.