Optical determination of L-tyrosine based on eggshell membrane immobilized tyrosinase

An optical biosensor based on the eggshell membrane immobilized tyrosinase is described for the detection of L-tyrosine (L-Tyr). The detection scheme was based on the measurement of absorption value of color adduct resulting from the reaction of 3-methyl-2-benzothiazolinone hydrazone and dopa-quinone produced from the enzymatic oxidation of L-Tyr. The prepared biosensor demonstrated optimum activity at pH 7, optimum temperature range of 20-40 degrees C and a linear response for the L-Tyr concentration in range of 5-200 microM. It also showed good operation stability for repeated measurements (over 300 times) and storage stability after it had been kept at 4 degrees C for 3 months.