Effect of setpoint on L-lysine fermentation

In control of a bioprocess, setpoint of fed-batch fermentation processes ha s a great influence on both the cost and the operating efficiency. Determin ation of a setpoint depends on the system and objective function. This work investigates two operating conditions for a fed-batch culture of L-lysine production. One is to maintain the reducing sugar concentration (RSC) on a constant setpoint, whereas the other has a piecewise variation of the RSC s etpoint. Productivity, yield, and a cost function are employed to evaluate the performance of different setpoints on the fermentation process. Constan t setpoint which is commonly used in fed-batch culture is not the best appr oach in L-lysine fermentation. Piecewise variation of setpoint shows that t he better policy is to set the RSC at a higher concentration in the early c ell growth stage then to decrease the RSC to a lower level.