Novel Amperometric Tri-Enzyme Biosensor for Lysine Determination in Pharmaceutical Products and Food Samples

An enzyme-based amperometric biosensor was developed for the determination of the lysine content of pharmaceutical products, food and feed samples. Lysine decarboxylase (EC 4.1.1.18) from Bacterium cadaveris was coupled with diamine oxidase (EC 1.4.3.6) from Pisum sativum and horseradish peroxidase (EC 1.11.1.7). The enzymes were co-immobilized on a graphite electrode with an Os polymer. The biosensor worked in flow injection analysis system (FIA). Optimal working conditions were pH 7.0 and −50 mV potential vs. Ag/AgCl. The linear measuring range was 0.005–0.500 mM. Different pharmaceutical products and feed samples were analysed by the lysine biosensor and by HPLC method for validation.