A new biosensing flow injection method for the determination of -amylase activity has been introduced. The method is based on the
analysis of maltose produced during the hydrolysis of starch in the presence of -amylase. Maltose determination in the flow system was
allowed by the application of peroxide electrode equipped with an enzyme membrane. The membrane was obtained by immobilisation of
glucose oxidase, -glucosidase and optionally mutarotase on a cellophane, co-crosslinked by gelatin-glutaraldehyde together with bovine
serum albumine. -Glucosidase hydrolyses maltose to -d-glucose, which is converted to -d-glucose by mutarotase. -d-Glucose is then
determined via glucose oxidase. The new biosensor has the limit of detection of 50 nmol l−1 maltose, which means 2 nkat ml−1 in -amylase
activity units, when the reaction time of amylase was 5 min (determined with respect to a signal-to-noise ratio 3:1). When the reaction time
of -amylase was 30 min, the limit of detection was 0.5 nkat ml−1. A linear range of current response was 0.1–3 mmol l−1 maltose, with a
response time of 35 s. The biosensor was stable at least two months and retained 70% of its original activity (with mutarotase the stability
is decreased to 3 weeks). When the enzyme membrane was stored in a dry state at 4 ◦C in a refrigerator, the lifetime was approximately 6
months (with mutarotase only 3 months).
© 2004 Elsevier B.V. All rights reserved.