AbstractIn this study, a mathematical model has been developed to evaluate the performance of industrial‐scale bioethanol production from molasses by Saccharomyces cerevisiae in a series of bioreactors operated in continuous mode. The model was based on three simple metabolic pathways in the yeast including molasses fermentation, molasses oxidation, and ethanol oxidation. The model parameters were estimated using the AQUASIM software by minimizing the error between measurements and calculated results. Results show that the model predictions agree well with the experimental results. The model is a useful tool to predict volumes, levels, discharge flow, bioethanol, and biomass concentrations in each bioreactor during the process. As it is not practical to make changes in steady‐state continuous operation processes, the model can also be used to optimize the process performance and to increase the biomass and ethanol yields. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd