Next generation bioreactor design for gas fermentation

  • Fortschrittliches Bioreaktordesign für die Gasfermentation

Bongartz, Patrick; Wessling, Matthias (Thesis advisor); Blank, Lars M. (Thesis advisor)

Aachen : Aachener Verfahrenstechnik (2023)
Book, Dissertation / PhD Thesis

In: Aachener Verfahrenstechnik series - AVT.CVT - chemical process engineering 38 (2023)
Page(s)/Article-Nr.: 1 Online-Ressource : Illustrationen, Diagramme

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2023

Abstract

Bioreactors are the production units of an expansive variety of high-value products in the pharmaceutical and biotech industry. They enable the efficient cultivation and expansion of bacteria, fungi, plant and animal cells. Products of these life forms e.g., proteins as enzymes, therapeutic molecules, the cells themselves, can be exploited for industry and medicine. Present methods of bioreactor aeration cannot provide high gas input at physiologic mixing conditions. Bioreactors can provide high oxygen transferrates (OTRs) only with accompanying high shear forces, which results in a drawback in several process due to the shear stress on the sensitive organisms. Additionally, foam formation, caused by the bubbles and surface active ingredients of the fermentation broth, lowers the vessels available reaction volume. To overcome this challenges, aim of this work is the development of a technology for the bubble-free aeration of microbial fermentations. Due to the diffusive gas input by usage of membrane aeration, bubble usage or formation should be avoided. As none of the recent membrane aeration technologies fulfill the oxygen demands of a microbial process, novel in situ membrane aeration approaches were designed and tested. Therefore, an aeration membrane originally used in medical application, and CFD simulations were utilized to gain an optimized module architecture. With a static membrane module with air, an OTRmax of 5.7 mmol L−1 h−1 was reached, what is 475% more then in commercially available membrane aeration modules. For intensification of a benchmark bioprocess for production of biosurfactants (Rham-nolipids, RL), the static membrane aeration module was additionally equipped with a cell-retention membrane. This cell-retention enables the direct, in-line transfer of the fermentation broth to a solvent extraction setup. A foam-free air aeration with parallel product extraction could be achieved for 46 hours by this system. To further improve the gas transfer performance, a dynamic membrane module was de-signed, combining the stirrers and the aeration function. The membrane module stirrer(MemStir) enables an OTRmax of 175 mmol L−1 h−1. Versatility of the MemS is shown by RL fermentation with Pseudomonas putida in batch and fed-batch. A direct comparison with a bubble aerated cultivation was made and hurdles in product analytics and downstreaming due to the antifoam are presented. A space-time-yield (STY) up to 124 mgRL L−1 h−1 was reached with the MemStir. This STY is almost identical with recent state-of-the-art fermentation approaches for RL synthesis, but with a significantly less complex operation. Beyond rhamnolipid production, this thesis discusses the applicability of the presented MemStir for the cultivation of vulnerable cells like animal cells. The CFD results indicate physiological flow conditions and oxygen supply with reduced harm to those cells.

Institutions

  • Chair of Chemical Process Engineering and Institute of Process Engineering [416110]

Identifier

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