Selective biosensing of L-lysine by a low-temperature flow-injection technique using an immobilized lysine oxidase reactor

An automated flow-injection analytical system, equipped with an immobilized L-lysine-alpha-oxidase reactor (stable for over 6 months) and having a hydrogen peroxide electrode in the manifold, was developed for biosensing L-lysine. A substantial improvement in the selectivity for lysine was achieved by lowering the system temperature to 10 degrees C; the sensor response was linearly dependent on the L-lysine concentration (from tens of mu M to mM order). The analytical results were verified by HPLC using protein hydrolyzates as test solutions comprising various interfering amino acids. By the aid of an in-line filter, the leaching of lysine from L-lysine-enriched fish feed into an aqueous buffer was automatically monitored.