In recent years it has been acknowledged that to significantly improve biological system performance and productivity, control, including optimal control, should be implemented online. The dynamics of biological processes are highly non-linear and key variables are difficult to measure. As an aid to contributing solutions to the twin difficulties of complex dynamics and measurement difficulty a relatively simple mathematical model has been developed for the purpose of evaluating optimal controllers. In this paper a simulation of fed-batch fermentation is developed which includes the no-linear dynamics of the process using single-term Haar wavelet series (STHW) method.