Bioreactor processes based on disposable materials for the production of recombinant proteins from mammalian cells

The objective of industrial cell culture technology is to produce high value-added therapeutic proteins that are well suited for the treatment of infectious diseases, cancer, and autoimmune diseases. Nowadays, an important focus is the reduction of the time and costs from the discovery of the candidate molecule to the full-scale production. Relying on enabling technologies is critical for meeting this objective. Simultaneously, novel technologies are expected to increase the clinical and commercial success rates. In recent years, new concepts based on innovative disposable materials emerged and appeared to be promising alternatives to standard bioprocessing equipment. This thesis work was focused on the use of such disposable compounds in mammalian cell culture applications, particularly for the containment of the cells, and was aimed at demonstrating their benefit in terms of cost-effectiveness, ease-of-use and flexibility. First, a novel disposable packed cell volume tube was shown to be ideal for the quick and reliable assessment of biomasses. A characterization and validation of the measurement system demonstrated that it could replace time-consuming and less accurate cell counting methods. Then, to determine the appropriate growth conditions for cells in culture, small-scale single-use tubes were orbitally agitated with conventional lab shakers. This approach was found to be well-suited for multi-parameter optimization strategies. A systematic characterization of the liquid mass transfer in shake tubes proved that sufficient oxygen was available even at cell densities beyond 1 ×107 cells mL-1. Non-invasive optical methods were used to assess the dissolved oxygen variations in various orbital shake vessels, from the milliliter to the multi-liter scale. This simple and yet powerful cultivation principle, orbital shaking, was scaled-up to pilot and production scales. To match the requirements in terms of oxygen transfer at larger scales, a given airflow was provided to replace the gas in the headspace. When required, the airflow was enriched with oxygen. At scales above 20 L, sterile disposable cell cultivation bags were used to contain the cells. Combining orbital shake technology and disposable cell culture bags with a cylindrical shape was promising, both in terms of efficiency and ease-of-use. Prototype shake bioreactors of 200 L and 1'500 L were designed, constructed and operated with maximal cell densities up to 5-7 ×106 cells mL-1 in batch cultivations of CHO cells. The benefits in terms of time and cost savings were even more obvious when novel shake bioreactors were compared with standard stirred-tank bioreactors. This was shown in a realistic optimization, scale-up and production sequence. Most importantly, this work established that orbital shake technology, unlike other disposable cell cultivation systems, can be used for a wide range of operating scales, from only a few milliliters for optimization purposes up to production scale.

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