Andrew P. Fordyce
Ph.D., University of Texas at Austin, 1991
As a means of comparison between the segregated modelling approach and more common fermentation models, a structured model has been adapted to the bacitracin system. The comparison model utilizes a two-compartment age model to describe cell growth, differentiation and bacitracin production.
Batch, steady state, and step-test fermentation data from a laboratory-scale fermentor have been incorporated into a maximum likelihood parameter estimation scheme for model identification. Confident estimates of the growth and differentiation parameters have been obtained for the segregated model using available measurements. However, the insensitivity of the bacitracin data to the production function only allowed for confident determination of a constant antibiotic production coefficient.
In contrast to the segregated model, the structure of the comparison model prevented complete utilization of the available measurements in the parameter estimation scheme. This created a situation in which the information provided by the applicable measurements was insufficient for confident determination of the model parameters. The two-compartment age model was also unable to adequately describe the delay between fermentor inoculation and the appearance of antibiotic.
Open-loop optimal control studies were utilized to compare the suggested control policies of the two models. The computed strategies were significantly different, with the segregated model suggesting a non-batch feeding policy that predicts improved antibiotic yield of 30% over the comparison model batch policy.
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University of Wisconsin
Department of Chemical Engineering
Madison WI 53706