Sterilizable enzyme electrode

Fig. 75. Construction of a sterilizable enzyme electrode for the determination of penicillin. A flat glass electrode, B reaction chamber containing enzyme, C dialysis membrane, D holder. (Redrawn from Enfors, 1987).

These examples indicate the in situ applicability of enzyme electrodes however, numerous problems have still to be solved. At present, coupling of enzyme sensors for fermentation control in a bypass arrangement appears to be more favorable [412]. Following this concept, an invertase thermistor incorporating a sterilizable filter unit has been developed [413] for the monitoring of alcoholic fermentation by immobilized yeast cells. Another thermistor has been successfully used for on-line glucose measurement under real cultivation conditions of Cephalosporium acremonium [414]. Similar calorimetric devices are suitable for other fermentation processes and in environmental analysis. 

Potentiometric penicillin sensors are mainly based on glass electrodes working with free enzyme or with enzyme included in an electrode cover. In the first penicillin electrode, (5-lactamase was directly photopolymer-ized in acrylamide on the electrode (Papariello et al., 1973). Enfors and Nilsson (1979) designed a sterilizable penicillin sensor where a solution containing (5-lactamase was pumped into a reaction chamber in front of a flat glass electrode, after sterilization of the electrode (Fig. 75). 

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