On-line implementation of decoupled input-output linearizing controller in Baker's yeast fermentation

Baker's yeast fermentation is influenced by the relative concentration of glucose and dissolved oxygen (DO) in the reactor. The process is sensitive to the oxidative capacity of the cells and exhibits a range of metabolic regimes depending on available glucose and oxygen. The time profiles of cell mass, glucose, ethanol and DO concentrations possess strong nonlinear characteristics. A decoupled input-output linearizing controller (DIOLC), which exhibited satisfactory performance in simulation experiments, was implemented online for validation. Our results showed that the DIOLC was capable of negating the interaction between glucose and dissolved oxygen, and executed satisfactory control action in experiments carried out in a 5 liter bioreactor. The performance of DIOLC was better compared to that of a PID controller implemented under identical test conditions.