Jeongseok Lee

Control of fed-batch fermentations.

Fed-batch fermentation is used to prevent or reduce substrate-associated growth inhibition by controlling nutrient supply. Here we review the advances in control of fed-batch fermentations. Simple exponential feeding and inferential methods are examined, as are newer methods based on fuzzy control and neural networks. Considerable interest has developed in these more advanced methods that hold promise for optimizing fed-batch techniques for complex fermentation systems.

PID controller tuning for integrating and unstable processes with time delay

A new method for PID controller tuning based on process models for integrating and unstable processes with time delay is proposed in this paper. The proposed method is an extension of the PID controller tuning method by Lee, Lee, Park and Brosilow (1998) to general unstable and integrating processes with time delay. The proposed method is simpler to use because the proposed method is an explicit tuning method compared with other frequency response methods. Closed-loop responses tuned by the proposed method are compared with those of existing methods. The results show that the proposed tuning method gives better closed loop performance than the existing methods.

Fed-batch culture of Escherichia coli W by exponential feeding of sucrose as a carbon source

Fed-batch cultures ofEscherichia coli W were carried out in a chemically defined medium containing sucrose as a sole carbon source. The substrate feed rate was changed every 30 minutes based on the immediate off-line analysis of medium. When the target specific growth rate was set at 0.15 and 0.2 h−1, the final cell concentrations of 105 and 110 g dry cell weight/L were obtained in 25 and 20 h, respectively.

An on-line batch span minimization and quality control strategy for batch and semi-batch processes

Abstract A novel strategy is proposed to minimize the operation time of batch and semi-batch processes. The proposed on-line strategy is based on linear regression models and employs a cascade control structure in which the primary controller calculates an optimal operation profile for the secondary controller to follow. A special feature of the proposed on-line strategy is that it conducts run-wise information feedback and achieves the attainable minimum operation time as the batch run is repeated despite model uncertainty. The performance of the proposed strategy is illustrated through simulation studies involving an exothermic batch reactor and a semi-batch reactor producing 2-acetoacetyl pyrrole.

An On-line Batch Span Minimization and Quality Control Strategy for Batch and Semi-Batch Processes

Abstract A novel strategy is proposed to minimize the operation time of batch and semi-batch processes. The proposed on-line strategy is based on linear regression models and employs a cascade control structure in which the primary controller calculates an optimal operation profile for the secondary controller to follow. A special feature of the proposed on-line strategy is that it conducts run-wise information feedback and achieves the attainable minimum operation time as the batch run is repeated despite model uncertainty. The performance of the proposed strategy is illustrated through simulation studies involving an exothermic batch reactor and a semi-batch reactor producing 2-acetoacetyl pyrrole.