In this study, a semi-structured model for the growth and production of lactase in an aerated bioreactor by Kluyveromyces marxianus, growing on cheese whey, was developed. Three modes of culture, consisting of batch, fed-batch and a controlled-release system were investigated. Modeling was based on three metabolic pathways, representing the growth of Kluyveromyces marxianus. Lactose and oxygen consumption, cell growth, and also lactase and ethanol production rates were determined in the model. Induction was considered as the governing mechanism for enzyme production. The model showed good agreement with the experimental data in batch and fed-batch cultures. Controlled-release system is a...