Optimal control strategies for simultaneous saccharification and fermentation of starch

Design and analysis of optimal control strategies for three types of inhibi tory fed-batch bioprocesses have been discussed. These are simple saccharif ication (SS) of starch to glucose, simple fermentation (SF) of derived gluc ose to lactic acid (LA) and simultaneous saccharification and fermentation (SSF) of starch to LA. Various optimal feeding strategies have been investi gated for the SSF process by manipulating starch addition rates. To avoid t he complexity of solving a singular problem, the starch addition rates are expressed in terms of the broth volume, which is used as a control variable . The optimization strategy is thus solved in a nonsingular framework. Expe rimental studies carried out using the results of the optimization demonstr ated the accuracy and utility of the approach. An increase of 20% in lactat e productivity was obtained by operating the SSF process in a fed-batch mod e. The focus of all the optimization studies has been to improve the perfor mance of the SSF process. Optimal control of starch additions in the fed-ba tch process gave improved performance of the SSF process. (C) 2001 Elsevier Science Ltd. All rights reserved.