In-line determination of metabolites and milk components with electrochemical biosensors

Electrochemical biosensors for lactate, pyruvate and ?-hydroxybutyrate based on oxygen, hydrogen peroxide, and NADH sensors coupled with oxidase and dehydrogenase enzymes were developed and used in conjunction with an artificial pancreas in experiments with extracorporeal circulation. Such procedures allow the fate of these species involved in glucose metabolism to be clarified during insulin treatment of diabetic patients. Studies with a glucose oxidase electrode for in-line determination of glucose produced by hydrolysis of cellobiose in a bioreactor are reported; for the determination of glucose in the presence of high concentrations of cellobiose, the purity of glucose oxidase is important in obtaining linear calibration plots. Impurities like amylase, maltase, invertase, and galactose oxidase, which are usually present in commercial preparations of glucose oxidase, must be absent. Another application is the amperometric determination of lactose, lactate and glucose in milk samples by using a hydrogen peroxide sensor coupled with ?-galactosidase, lactate oxidase and glucose oxidase. The procedures outlined are simple and the short response times enable milk to be monitored during processing. © 1988.