Simulation of Yeast Fermentation Process Using Kinetic Unstructured Models

Abstract

The modeling of biological systems is a very interesting field that presents an extremely delicate task because, unlike physics, there are no accepted and universally recognized laws characterizing the evolution of the biological phenomena. The main objective of this chapter is to describe the modeling of yeast fermentation process using some unstructured mathematical models. An experimental application has been made using the yeast P. caribbica as an agent for the bioconversion of inulin into bioethonol which is considered as potential substitute for fossil fuels. The bioethanol batch fermentation of P. caribbica strain was carried out in flasks and bioreactor (20L); under optimal conditions of ethanol production (40 g/L of inulin, 4g/L of yeast extract and 4g/L of peptone pH 5 and 37°C). The production of ethanol has reached after 72h, 12.6 g/L in flasks (our previous study) and 14g/L in bioreactor conditions. Furthermore, for inulinase (the enzyme that catalyzes the degradation of inulin) production, significant amounts have been found after 96h in the bioreactor (20L), reaching 55.47 IU/mL (This fining was illustrated for the first time in our work). The adequacy of the three mathematical models, i.e., the logistic equation for growth; the Luedeking- Piret equation for ethanol production; and modified Leudeking- Piret model for substrate consumption has been proven in the case of the in flasks fermentation experiment whose the results obtained were almost the same compared to those found in the bioreactor (20L) fermentation process. In conclusion, the above sited unstructured mathematical models could be used to predict the fermentation process in a bioreactor (20L).