Model of quartz crystal microbe growth sensor and its application to estimation of microbial populations in mineral waters

A simple, rapid, on-line quartz crystal sensor is proposed for monitoring viscosity changes in culture medium caused by microbe growth. A model based on frequency response of the crystal to microbe growth is presented. Optimum culture conditions including medium composition, temperature and acidity are investigated. Calibration curves relating the lag times of the frequency growth curves to initial bacteria concentrations in sample solutions are generated for frozen E. coli samples and contaminated waters. The linear range is from 102 to 106 cells/ml. This method is applied to evaluate microbial levels in mineral waters. Results are in good agreement with those obtained by standard pour plate method.