ABSTRACT
This chapter addresses the issue of bioreactor operability when applied to a continuous prefermentation of cheese culture. Cheese production is traditionally a batch process, but with an-ever increasing cheese consumption, the mass production of cheese is of great interest to the dairy industry. For this reason, the study of a potential continuous process for cheese production would help to achieve two goals: The first is to study the improvement in the bioreactor productivity while the second objective is to analyze the potential operating problems that may be inherent in the continuous bioprocess. A number of models were developed in the literature for cell growth and lactic acid production [90, 178, 267, 332, 376]. These models were, however, limited to either constant or optimal controlled pH values. These models may present some shortcomings since the cheese prefermentation process is known to be a hydrogen ion dependent process, as the pH of milk changes with cell growth and lactic acid production. Funahashi et al. [116] proposed a kinetic model that can predict both growth and lactic acid production in prefermentation without external pH control. The proposed model was shown to simulate uncontrolled pH experiments. The same authors, in another study [117, 205], carried out a local stability analysis for the model and showed that for given values of kinetic parameters, the model can predict static multiplicity. The authors also studied the case when a seed tank was added to the bioreactor. Their analysis showed that the addition of the seed tank provided a stabilizing effect on the bioreactor dynamics.
