Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Chemical and Biomolecular Engineering

Committee Chair/Advisor

Dr. Sarah W. Harcum

Committee Member

Dr. Marc Birtwistle

Committee Member

Dr. Jessica Larsen

Committee Member

Dr. Kim Paul


Chinese hamster ovary (CHO) cells are among the most commonly used mammalian cell lines for the production of recombinant therapeutic proteins due to ease of culturing and humanlike post-translational modification capabilities. However, when compared to microbial systems, CHO cell line growth and productivity is relatively low. As the demand for monoclonal antibody (mAb) treatments continues to rise, it is critical to explore modalities for improved growth and productivity in CHO cell cultures, with the goal of increased protein concentrations and maintained product quality. Though some mechanisms for improved productivity, including temperature and cell culture media formulations, are relatively well understood; others such as feeding strategies, pH, and pCO2 dynamics are more elusive.

The objective of this work is to establish a broader understanding of cell culture levers that impact CHO cell growth, productivity, and product quality in fed-batch cultures. This work evaluates the impacts of a glutamate-driven feeding strategy, a dynamic pH profile, and a HEPES/MOPS buffering system on growth, productivity, and product quality attributes such as glycosylation and charge variants for a CHO-K1 cell line. The glutamate-driven feeding strategy was used to diminish the negative effects of overfeeding that often occur with a typical daily bolus feeding strategy. The results indicated that amino acid driven feeding has the potential to increase the stationary phase duration, increase overall culture duration, decrease metabolic waste products, and promote more favorable glycosylation profiles. Though often overlooked, overfeeding also increases dissolved CO2 (pCO2) in cell culture due to higher cellular metabolic rates. The dynamic pH profile was used to decrease pCO2 in cultures, as CO2 is often used for set-point pH control. The CO2 used for pH control coupled with the CO2 produced by the cells often leads to decreased growth and productivity. The results showed that a dynamic pH profile is able to increase cell specific and overall culture productivity via decreased pCO2. A HEPES/MOPS buffering system was also explored as a way to decrease pCO2 in the cultures. This alternative buffering system resulted in increased productivity while maintaining critical quality attribute (CQA) benchmarks. Overall, this work presents several mechanisms for improved growth, productivity, and product quality in fed-batch CHO cell cultures. iii



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