Stochastic stability and observer design for the lac operon model

The aim of this study is to investigate the stability properties of a model of the lac operon enhanced with stochastic perturbations. New sufficient conditions of exponential mean square stability are obtained analytically for this model and threshold values derived. For regulatory networks, an observer method for the dynamic of the lac operon model is employed, that uses the measured input and output of the model, to estimate proteins concentration that cannot be easily measured experimentally. Numerical investigations of the bistability and the observer are performed with respect to lactose concentration and noise terms. We demonstrate that the noise affects the behaviour in the bistable region.