Optimal operation processes of discrete-continuous biochemical processes

Biohemical processes and so-called hybrid biochemical processes, carried ou t in integrated unit operations such as membrane bioreactors, have found nu merous applications in food and pharmaceutical process industries. However, such processes have hardly been investigated comprehensively. Dynamic mode ling and especially dynamic optimization attempts were restricted because t hese unit operations combine continuous and discrete dynamic behavior and c ontain time and state events. In this paper we present a robust model of a process of high industrial significance, namely citric acid production in a membrane bioreactor, as well as a successful application of control parame terization numerical optimal control techniques to the fed-batch bioreactor and a membrane bioreactor. In order to evaluate the advantages and disadva ntages of the design alternatives, the incremental objective function betwe en batch and fed-batch, batch and different operations in a membrane biorea ctor was formulated in terms of profit maximization. The determination of t he optimal performance for the fed-batch fermenter and membrane bioreactor requires the solution of multiple optimal control problems, namely determin ing optimal feed and inlet concentration profiles, initial conditions and a production time. We show how the systematic combination of rigorous mathem atical modeling: the integration of design and operational decisions and in novative discrete-continuous dynamic optimization techniques allow the gene ration of optimal designs and operating policies for hybrid biochemical pro cesses that increase the profit of important production processes such as c itric acid production. (C) 2000 Elsevier Science Ltd. All rights reserved.