The development of an amperometric microbial biosensor using Acetobacter pasteurianus for lactic acid

A microbial biosensor, using Acetobacter pasteurianus cells and an oxygen electrode, was developed for the determination of lactic acid. The bacterial cells were retained on a nylon membrane and attached to the surface of the oxygen electrode. In view of response time, stability and sensitivity, the biosensor performed best at 26°C and in pH 6 phthalate buffer containing magnesium sulfate. The activity of the retained cells was stable for approximately 170 h and was regenerable. The biosensor exhibited a hyperbolic response to both D- and L-lactic acid in the range of 10 −4 M to 25 × 10 −3 M. However, in the range 10 −4 M to 15 × 10 −4 M the response was linear. The microbial biosensor was applicable for detecting lactate concentration in yogurt and milk, since it was not sensitive to lactose, sucrose and glucose — three major components of such dairy products.