Browsing by Subject "Wachstumsrate"

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Temperaturgesteuerte Zellzahlregelung für Bioreaktoren
(2021) Loges, Karin Martina; Hitzmann, Bernd
Biopharmaceutical cell culture processes are multi-stage processes. Starting with low cell numbers and small culture volumes, the upstream process takes place step by step in a reactor cascade with increasing volume. To achieve constant product quality and high reproducibility, each reactor must be seeded with a defined initial cell concentration and all cultures must show very similar growth rates. However, batch to batch variations of growth rates can occur in biological systems and disrupt the reproducibility of the inoculation with defined cell concentrations. In order to control the growth rate and thus increase the reproducibility from batch to batch, a self-adapting cell number controller was developed. This controller can be rapidly introduced in a typical industrial (biopharma) environment. At the beginning of the process, the user specifies the desired seed cell concentration and the point in time at which this cell concentration should be reached. In the following, the cell number controller automatically regulates the growth rate of the cells during the process and leads it to the specified process end parameters. The regulation of the cell growth rate is achieved with adjustment of the process temperature. In the development phase of the cell number controller, a converted reactor system was adjusted and qualified. The temperature dependency of the biomass probe was examined. After that, the dependence of the cell growth rate on the temperature was analysed, described in the form of a mathematical model and implemented in a control algorithm. The required temperature is calculated with the aid of a numerical optimization process, using the previously derived mathematical model of the temperature-dependent growth rate, the online measured values and the specifications of the user. In order to achieve greater flexibility within the upstream process and to be able to react to disruptions in the process flow, it is also possible to dynamically adjust the target parameter, set by the user at the beginning, during the running process. To optimize the controller, it was analysed how the mathematical algorithm can be adapted to different cell clones and which tests are absolutely necessary to determine the cell specific, temperature-dependent growth rate. In this context, a self-learning algorithm was implemented so that it is now possible to use the controller without preliminary tests and to ensure constant control quality in the event of possible changes in the cell growth of a cell clone. During this research project, the functionality of the cell number controller, such as the changes in the process end parameters during the ongoing process and the iterative-adaptive optimization of the mathematical algorithm on different cell clones, could be verified experimentally. The biological reactions of the cells to the temperature changes within the cell number-controlled precultures and within the subsequent production stage were also analysed. Furthermore, a possible influence on the quantity and quality of the products was examined. All examined biological reactions of the cells during the cell count regulation showed a reversible behaviour, which are normalized in the following process steps at 37 °C within two days. In addition, no negative influence of the cell-number-controlled preculture on product quality and quantity could be determined. In summary, a functionally adaptable cell number controller was developed and tested with two different CHO cell clones for a possible influence on cell metabolism, apoptosis, product quantity and Quality.