DEVELOPMENT OF SENSOR SYSTEMS BASED ON ENZYME-MODIFIED FIELD-EFFECT TRANSISTORS FOR PROCESS CONTROLIN BIOTECHNOLOGY

Sensor prototypes for the determination of urea, glucose, penicillin G, penicillin V and cephalosporin C were developed. Hydrogen ion-sensitive field-effect transistors (pH-FETs) served as transducers in these biosensors. The pH-sensing surface of the pH-FETs was modified with membrane layers containing an enzyme. Urease, glucose oxidase, penicillin G amidase, penicillinase, cephalosporinase proved to be suitable enzymes. The enzyme sensors had a dynamic Tange of two orders of magnitudesubstrate concentration. The Tesponse times varied between 50 and 150 seconds, the glucose sensor prototypes showed slower responses. The enzyme-FETsfunctioned well for 10 - 100 days (storage at room temperature) depending onthestability of the enzyme. pH andbuffer capacity of the sample strongly affect the performance characteristics of these sensors. Other parameters are of minor importance. As an example,the results for penicillin G amidase-FETsare described. Urease-, penicillinase-, and penicillin amidase-FETs were successfully integrated as detectors in a flow injection analysis system (FIA). Using a FIA equipped with a penicillin-amidase-FET,penicillin G concentrations from 1.5 to 50 mM could be measured reproducibly, also in microfiltrated broth from a Penicillium chrysogenum cultivation