Tools accelerating the development of unconventional bioprocesses

  • Werkzeuge zur beschleunigten Entwicklung unkonventioneller Bioprozesse

Geinitz, Bertram Michael; Büchs, Jochen (Thesis advisor); Agler-Rosenbaum, Miriam (Thesis advisor)

Aachen : RWTH Aachen University (2023)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2023


Unconventional microbial systems, such as cocultures or gas utilizing biocatalysts, bear great potential in converting residues or complex substrates. This thesis demonstrates three approaches for the characterization of novel systems, as new techniques for process monitoring and cultivation are required to develop such processes.Continuous data of the individual biomass concentrations are necessary to characterize and optimize coculture processes. Up to now, primarily offline methods with low temporal resolution have been applied to determine the culture composition. Therefore, a noninvasive online monitoring tool based on scattered light spectra was developed for microtiter plate cultivations. A coculture containing Lactococcus lactis and Kluyveromyces marxianus was cultivated to demonstrate the tools’ potential. Via partial least squares regression of scattered light spectra, the online determination of the individual biomass concentrations is possible. The results were successfully validated by a Coulter counter-analysis, taking advantage of the different cell sizes of both organisms. The findings prove the applicability of the new method to follow the dynamics of cocultures in detail. To characterize cocultures without complex equipment and know-how, a microtiter plate for the spatially separated cultivation was designed. Via microfiltration channels in the bottom plate, metabolites can be exchanged between the two linked wells. The mass transfer was characterized in abiotic experiments and compared to modeled cocultivations. It was revealed that the cocultivation in the Link-Plate significantly increases the process time; therefore, the metabolite exchange between the linked wells needs to be increased in the future.The biocatalytic utilization of methane originating from waste streams or renewable resources can reduce the carbon footprint of production processes. However, gas fermentation processes are often characterized in serum bottles leading to a changing availability of gaseous substrates over time. Since gas consumption and production rates are thus unknown, knowledge gain is limited. Therefore, Methylococcus capsulatus, an aerobic methanotrophic bacterium, was cultivated in semi-continuously ventilated shake flasks allowing for simultaneous monitoring of the respiratory activity. The methane and oxygen concentrations for ventilation of the shake flasks were calculated to omit explosion hazards while supplying as much substrate as possible. It was demonstrated that the device substantially supports the characterization of aerobic methane utilizing microorganisms.


  • Chair of Biochemical Engineering [416510]