Heuristic feed rate profiles for optimal yield and productivity of fed-batch bioprocesses

The optimization of two important classes of fed-batch fermentation process es with respect to the limiting substrate feed rate is considered:(i) growt h of one biomass on one limiting substrate, and (ii) growth and product for mation on one substrate. For these two types of bioprocesses, two different performance criteria are compared: yield and productivity. Heuristic feed rate profiles are derived based on (i) the optimal control solution accordi ng to the minimum principle, and (ii) the qualitative behavior of the speci fic rates for growth and possibly product formation. For biomass production processes, it is illustrated that the heuristic strategy coincides exactly with the optimal control solution, while its structure is independent of t he performance index considered. For product formation processes, it is ill ustrated that the same heuristic approach can be used to optimize both yiel d and productivity in spite of the well known conflict between them.