There have been numerous reports of spontaneous oscillations occurring in chemostat cultures of yeast Saccharomyces cerevisiae. A cybernetic model of yeast metabolism has been used to predict the appearance and disappearance of these sustained oscillations in response to changes in the chemostat operating parameters (dilution rate (1/hour), oxygen transfer coefficient (1/hour), inlet glucose concentration (g/l), and inlet ethanol concentration (g/l)). This Demonstration allows the user to investigate how bioreactor concentrations of cell mass (gdw/l), dissolved oxygen (mg/l), glucose (g/l), ethanol (g/l), intracellular amounts of the carbohydrate mass fraction (g/g cdw), and three hypothesized enzymes are predicted to respond to changes in the operating parameters.