A new biosensor for specific determination of sucrose using an oxidoreductase of Zymomonas mobilis and invertase.

A new biosensor for specific determination of sucrose was developed using an oxidoreductase of Zymomonas mobilis and invertase. Cells of Z. mobilis were permeabilized with toluene in order to utilize the enzymes of glucose-fructose oxidoreductase and gluconolactonase inside the intact cells. Permeabilized cells and invertase were coimmobilized in a gelatin membrane, and a whole cell enzyme electrode was constructed by fixing the membrane on a pH electrode. The production of hydrogen ion was detected using the biosensor-connected microcomputer, and the concentration of sucrose was determined by using both the initial rate and the steady-state methods. Optimum conditions for biosensor response were pH 6.2 and temperature 35 degrees C. The effect of interfering compounds on the electrode response was investigated, and the interference by various sugars was eliminated by determining sucrose concentration using the steady-state method. The biosensor developed is simple and reproducible, and the calibration curve for sucrose is linear up to 70 g/L.