THE COMBINATION OF AN AMPEROMETRIC INTEGRATED GLUCOSE SENSOR WITH FLOW-INJECTION ANALYSIS FOR BIOPROCESS CONTROL

The on-line determination of glucose concentrations is of crucial importance for bioprocess control. Biosensors can offer decisive advantages, but only if they are treated as a component of a total analytical system. The glucose sensor we use is a miniaturized planar three-electrode structure with glucose oxidase immobilized on the electrode surface. The hydrogen peroxide produced by the enzymatic conversion of glucose is determined amperometrically. The performance of such a sensor is improved upon introduction into a flow injection analysis manifold, since this technique makes automatic calibration and sample preconditioning possible. Glucose is determined off-line and on-line during a yeast cultivation in conjunction with a reference method to compare data. However, matrix effects are still present, and signals due to interfering substances are significant at low glucose concentration levels. Different ways for eliminating these interferences and improving the stability of the enzymatic membrane are described.