Date of Award

8-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Electrical Engineering

Committee Member

Dr. Richard Groff, Committee Chair

Committee Member

Dr. Sarah Harcum

Committee Member

Dr. Yongqiang Wang

Committee Member

Dr. Adam Hoover

Abstract

The biopharmaceutical industry is constantly developing new recombinant Es-cherichia coli strains to bring new products to market. In early stages of development, small scale bioreactors are used to make the product and explore di˙erent growth pro-tocols. Researchers spend significant time finding a feed rate profile that will give fast growth and low byproduct accumulation. The objective for the controller pre-sented in this work is to achieve fast growth and low acetate accumulation for an E.coli fermentation. The controller does not rely on previous characterization data or models but on fundamental metabolic relationships between oxygen and glucose as dictated by the Crabtree e˙ect. The controller senses metabolic state using an on-line oxygen uptake rate (OUR) estimate and pushes the culture to the boundary of oxidative and overflow metabolism (BOOM). A simulated E.coli culture and biore-actor were constructed to test controller performance. Fermentation experiments compared the BOOM controller to an Exponential feed and a DO-stat controller. Using minimal knowledge about the strain, the BOOM controller kept an induced E.coli MG1655 pTVP1GFP strain growing near the boundary of oxidative and over-flow metabolism. The BOOM controller produced more recombinant protein than the Exponential feed controller and the DO-stat controller, even though the growth rate used by the Exponential feed controller was extensively researched by a previous group. In another fermentation, the temperature was lowered to incur a fast change in the E.coli metabolism. In all experiments, the BOOM controller demonstrated it could maintain fast growth and avoid inhibitory acetate concentrations while requir-ing minimal knowledge of theE.coli MG1655 pTVP1GFP strain. For laboratories which deal with many di˙erent strains and proteins, the BOOM controller would maximize protein production and speed up protocol development.

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