OPTIMAL ON-OFF CONTROL FOR FED-BATCH FERMENTATION PROCESSES

An optimal substrate feeding policy with on-off control is suggested for fed-batch fermentation processes described by differential-algebraic equations. With the on-off control parameterization, the optimization problem considered is a constrained finite-dimensional parameter selection problem that can be solved by constrained nonlinear programming methods. A unified algorithm for computing the gradients of the cost function and the constraints with respect to parameters are derived. The proposed optimal on-off feeding policy provides the advantage of easy implementation by low-cost actuators over the conventional continuous-feeding policy. For illustration, a fermentation process governed by product- and substrate-inhibited kinetics is chosen for this study. © 1990, American Chemical Society. All rights reserved.