Professor William A. Weigand

Weigand Ph.D., Illinois Institute of Technology, 1968

Room 1223B Chemical and Nuclear Engineering Building
E-mail: weigand@umd.edu
Phone: (301) 405-1916

Current Research Interests

Professor Weigand's research interests are biochemical engineering and process control. These areas involve the modeling, optimization, reaction engineering, and control of bioreactors. Specific problems involve kinetic modeling of cell growth and product formation for microorganisms which produce both primary and secondary metabolites. These models are used in optimization analysis to maximize bioreactor performance. The optimal operating procedures are then examined with the aid of computer simulation and experiments carried out with a highly instrumented, computer coupled fermentor. In addition, the use of techniques which permit optimal operation in the absence of complete variable measurement or inaccurate or changing process models are important research areas.

Modeling research involves the develop ment and use of: relatively simple structured models which describe protein expression; simplified metabolic models based on energetics which help to describe cell growth and product formation; neural network models which hold promise to describe complex industrial fermentations in situations where adequate models cannot be obtained by the more conventional approahces. In particular, energetic models ofE. coliwhich describe how the switch between respiration and fermentation is affected by glucose flux and dissolved oxygen is an active area. This type of model can be used to optimize product formation and develop procedures to control the process.

Weigand's r esearch interests also include new types of bioreactors and improved operating procedures. In particular, reactors and procedures for: unstable organisms (e.g., recombinant organisms, high yield mutants, etc.); product inhibited fermentations (e.g., solvents, antibiotics, etc.); substrate inhibited fermentations (e.g., growth on toxic chemicals) are all under investigation. In the area of substrate inhibition, an investigation of alternative reactor configurations for the bioremediation of toxic chemicals is currently under way.

In the area of process optimization and control, techniques of particular relevance to biological reactors are of interest. In addition to control with incomplete measurement, techniques for control and optimization in the presence of modeling error, for changing system dynamics, and for nonlinear interacting systems are important. In particular, optimization and control for fed batch and continuous reactors using neural network models for the process and/or the controller are active research areas. In particular, the use of neural networks for the adaptive optimization and control of continuous reactors is a current project. Also, the use of a network to synthesize the optimal input for a fedbatch reactor in a feedback form is under investigation. The list of selec-ted publications given below give some specifics of these ideas.

Selected Publications

Y.-F. Ko, W. E. Bentley, and W. A. Weigand, "An Integrated Metabolic Modeling Approach to Describe the Energy Efficiency of E. coli Under Oxygen-Limited Conditions: Cellular Energetics and Carbon Flux," Biotechnology and Bioeng. 42, pp. 843-853, (1993).

Y.-F. Ko, W. E. Bentley, and W. A. Weigand, "A Metabolic Model of Cellular Energetics and Carbon Flux During Aerobic E. coli Fermentation," Biotechnology and Bioeng. 43, pp. 847-855, (1994).

B. J. Sines, E. W. Teather, S. P. Harvey, and W. A. Weigand, "Investigation of Biological Reactor Design for Treatment of Methanol and Thiodiglycol Waste Streams," Applied Biochemistry and Biotechnology 45/46, pp. 881-89, (1994).

B. J. Sines, E. W. Teather, P. Wise, T.-S. Lee, M. Pham, W. E. Bentley, W. A. Weigand, and S. P. Harvey, "Investigation of Biological Reactor Designs for the Treatment of Compounds with Substrate Inhibited Growth Behavior," in Proc. 1993 ERDEC Sci. Conf. on Chemical Defense Research (Aberdeen Proving Ground, MD), pp. 445-451, (1994).

Q. Chen, W. E. Bentley, and W. A. Weigand, "Optimization for a Recombinant E. coli Fed-Batch Fermentation," Applied Biochemistry and Biotechnology 51/52, pp. 449-461, (1995).

Y. -F. Ko, W. E. Bentley, and W. A. Weigand, "The Effect of Cellular Energetics on Foreign Protein Production," Applied Biochemistry and Biotechnology 50, pp. 145-159, (1995).

M. Q. Pham, S. P. Harvey, W. A. Weigand, and W. E. Bentley, "Reactor Comparisons for the Biodegradation of Thiodiglycol, a Product of Mustard Gas Hydrolysis," Applied Biochemistry and Biotechnology, 57/58, pp. 779-789, (1996).

T. S. Lee, M. Q. Pham, W. A. Weigand, S. P. Harvey, and W. E. Bentley, "Bioreactor Strategies for the Treatment of Growth-Inhibitory Waste: An Analysis of Thiodiglycol Degradation, the Main Hydrolysis Product of Sulfur Mustard," Biotechnology Progress, 12, pp. 533-539, (1996).

T. S. Lee, W. A. Weigand, and W. E. Bentley, "Observations of Metabolite Formation and Variable Yield in Thiodiglycol Biodegradation Processes: Impact on Reactor Design," Applied Biochemistry and Biotechnology, 63/65, pp. 743-757, (1997).