A lactate sensor composed of lactate oxidase and a voltammetric device to determine hydrogen peroxide is used to determine the numbers of lactate acid produced in the bacteria. The system consists of a lactate sensor in a membrane filter for trapping lactic acid producing bacteria.
The principle of the system for the determination of cell numbers ia as follows: Lactic acid producing bateria produce mainly lactate as a metabolite from glucose. The rate of lactate production depends on the cell numbers retained on the membrane filter, when the glucose concentration of the sample solution is constant. Therefore, the current obtained from the lactate sensor is also affected by the cell number on the membrane filter. The system is suitable for the specific determination of lactic acid producing bacteria.