Studies on microbial biosensor for DL-phenylalanine and its dynamic response process

A biosensor for the determination of DL-phenylalanine, based on immobilized bacteria P. Vulgaris in calcium alginate gel coupled with an amperometric oxygen electrode, was designed and constructed. The effect of the culture medium, the response character of the electrode and its kinetic mechanism were studied, and the activity of phenylalanine deaminase was tested by biochemical method. The biosensor exhibited longer lifetime, higher sensitivity and faster response to the Phe in the linear range of 2.5x10(-5) to 2.5x10(-3) M for the optimum analytical performance. The relationship between the response velocity and the substrate concentration was also discussed. The results indicate that the dynamic response process of the reaction catalyzed by bacteria is similar to that by isolated enzymes. The apparent Michaelis constant, K-m(app), the apparent activation energy, E(n) and the temperature coefficient, Q(10) for deaminase in the immobilized bacterial membrane were calculated to be 2.0x10(-3) M, 49.5kJ/mol and 1.86 respectively.