Fast analysis of lysine in food using protein microwave hydrolysis and an electrochemical biosensor

A fast procedure for lysine analysis in food was developed by coupling in sequence a microwave protein hydrolysis technique with a lysine enzyme electrode. Protein hydrolysis was carried out in 6N HCl using sealed vessels located in a microwave digestion system. Parameters such as irradiation power, pressure, time and temperature were varied to select the best conditions for the hydrolysis. The hydrolysate was then analyzed for lysine using an electrochemical biosensor based on an amperometric H2O2 transducer and the enzyme lysine oxidase covalently immobilized on a preactivated polymer support. Analytical parameters, such as pH, buffer and measurement system were studied in order to eliminate or minimize the enzymatic interferences. Bovine serum albumin and two farro (T. dicoccum) meals (whole and sieved) were processed for lysine content. The analysis was carried out with this new procedure (microwave hydrolysis + biosensor) and by traditional hydrolysis coupled with ion-exchange chromatography (IEC). Results obtained with the two procedures correlated well.