Graduate Thesis Or Dissertation
 

Membrane and micro-sparging aerations in long-term high-density perfusion cultures of animal cells

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/4q77ft837

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  • The profile of the inner-tubing gas pressure for a tubular membrane aeration system was quantified. The correlations among the overall volumetric oxygen transfer coefficient (k[subscript L]a), the inner-tubing pressure, the tubing tightness, and the gas throughput are experimentally analyzed. A mathematical model was developed to describe the underlying phenomena. The results established the base for comparison with other aeration techniques. A novel method employing in situ laser imaging technology to monitor bubbles and cells, and analyze bubble size distributions in a micro-sparged bioreactor was developed. The effects of bioreactor operations on bubble size distributions were determined with following results: 1) Spargers with larger pores produced larger bubbles in most cases 2) Higher sparging rates resulted in bubble size increases up to 10% 3) Pluronic F68 shrank bubbles up to 30%. When the concentration of Pluronic F68 exceeded 1 g/L, no additional impact was observed. 4) Emulsion silicone antifoam up to 25 ppm had no impact on bubbles 5) Cell density (up to 22x10⁶ cells/mL) or culture age has no effect on bubble sizes In multiple 1 5-L long-term high-density cultures of animal cells, the correlations between sparging rate and cell damage for using 0.5 μm and 15 μm-pore spargers were quantified. At cell density of 2x10⁷ cells/mL, sparging above 0.025 vvm using the 0.5-μm sparger was detrimental to cells, while 0.054 vvm was detrimental for the 15-μm sparger. A model was developed to predict the rate of cell death resulted from cell-bubble interactions for high-density industrial animal cell cultures. The effect of high superficial velocity of sparging gas on cells at the sparger surface proved insignificant. A new dissolved CO₂ sensor proved to be reliable for long-term use in industrial perfusion cell cultures. A novel method for the control of dissolved CO₂ while simultaneously maintaining DO₂ and pH setpoints was developed. The continuous control of dissolved CO₂, DO₂ and pH is achieved by simultaneously adjusting the total sparging rate as well as the ratio of O₂, N₂ and CO₂ gas contents. This control strategy enables optimization of dissolved CO₂ in industrial culture processes and allows for improved cell growth and protein production.
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