High cell density fermentations of recombinant microorganisms using a pressurized, pilot scale bioreactor

  • Hochzelldichte-Fermentationen von rekombinanten Mikroorganismen in einem druckbeaufschlagten Bioreaktor in technischem Maßstab

Knabben, Ingo; Büchs, Jochen (Thesis advisor)

Aachen : Publikationsserver der RWTH Aachen University (2010)
Dissertation / PhD Thesis

Aachen, Techn. Hochsch., Diss., 2010

Abstract

As industrial fermentation processes mostly focus on producing high target concentrations of biocatalysts or pharmaceutical ingredients, it is important to investigate cell growth under high cell-density conditions. Thus, in this work different recombinant microorganisms (bacteria and yeast strains) were basically cultivated in a pressurized, pilot-scale bioreactor to high cell density. Focussing on high biomass concentrations, empirical (batch mode and fed-batch mode) and model-based process strategies (fed-batch mode) were investigated. Furthermore, in one case product concentration (pDNA-vaccine) conducted under pressurized conditions was directly compared to a non-pressurized process strategy (using oxygen-enriched air). Moreover, the highest ever shown process values for conventional online measurement techniques (capacitance and respiration activity) could be pointed out, validating viability of the microbial cultures during aerobic bioprocesses. Here, linear biomass/capacitance correlations up to biomass concentrations of 180 gL-1 and oxygen transfer rates up to 1 molL-1h-1 were reached. For batch and fed-batch processes it could be shown that increasing the head-space pressure in stirred bioreactors can be a practicable approach to provide the oxygen demand of extremely high cell-density cultures. Consequently, for reaching unusual high amounts of biomass or product, process strategies for high cell-density under increased head-space pressure could lead to a minimized bioreactor capacity utilization or minimized bioreactor size.

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