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Abstract
A simple, rapid and selective biosensor for reagent-less L-tryptophan determination has been developed. Tryptophan-2-monooxygenase was immobilized on silica gel. A Clark-type membrane O2 electrode was used as a physical transducer. A positive correlation between signal and L-tryptophan concentration was observed between 0.025 mM and 1.0 mM L-tryptophan. The sensitivity of the biosensor to L-phenylalanine was 30% and to L-methionine 6% relative to L-tryptophan, while there was no response to L-glycine, L-leucine, L-valine, L-isoleucine L-ornithine, L-alanine, L-proline, L-lysine and L-phenylglycine. The analysis time was 2 minutes, and the biosensor has retained activity for greater than 4 months. The biosensor was successfully used for L-tryptophan determination in the nutrition broth.
