Amperometric Bi‐enzyme based biosensor for the detection of lactose—characterization and application

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Abstract
Based on the glucose oxidase‐β‐galactosidase sequence an enzyme probe for the specific determination of lactose has been developed. β‐Galactosidases from different sources have been compared, the sensor containing β‐galactosidase from Curvularia inaequalis has been characterized in respect of optimal pH, enzyme loading, apparent activity and functional stability. The response of the bi‐enzyme probe depends linearly on lactose concentration between 0.02 and 3.00 mmol dm−3. The application to different milk and foodstuff samples resulted in good correlations toward enzymatic photometric (y = (0.956x‐1.67) mmol dm−3) and infrared detection (y = (1.0772x‐0.3909)%). Using a measuring frequency of 100 h−1 the serial imprecision is about 2% for diluted milk, urine, or foodstuff samples.