Nonlinear control of competitive mixed-culture bioreactors via specific cell adhesion

nonlinear control strategy is developed for competitive mixed-culture biore actors in which two cell populations compete for a common growth limiting s ubstrate, A stream is periodically removed from the.:reactor, and the two c ell populations are separated using specific cell adhesion. The steady stat e corresponding to the desired population fraction is stabilized by discard ing faster growing cells and recycling slower growing cells to the reactor. The recycle loop must be operated periodically to allow regeneration of th e adhesion column after each separation. As a result, the manipulated input is chosen as the sampling interval during which material is removed from t he reactor. The nonlinear controller is designed using a simplified dynamic model that assumes continuous separation of the cell populations; The cont roller is implemented by calculating the sampling interval that leads to th e same amount of material being removed from the reactor as that computed f rom the continuous control law. A nonlinear, closed-loop observer is used t o generate one-time-delay-ahead predictions of the measured cell concentrat ions and the unmeasured substrate concentration. The efficacy of the propos ed control strategy is evaluated via simulation.