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Bio0reactor modelling & control

Richards, Luke (2013) Bio0reactor modelling & control. Other thesis, Murdoch University.

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Bioreactors provide controlled environments for biological processes, and find many uses in industrial and research settings. Such bioprocesses often involve the cultivation of living cells which necessitates strict control of a range of biologically important parameters (e.g. temperature, pH, aeration) to ensure optimal growth and product yield. Bioreactors are therefore equipped with instrumentation to monitor and control a range of variables that allows precise regulation of the dynamic environment within the reactor vessel.

This project involved the use of the Murdoch University bioreactor to parameterise a growth model of baker’s yeast (Saccharomyces cerevisiae). The initial component of the project involved the setup, calibration and testing of the bioreactor and related instrumentation in a new, dedicated bioreactor laboratory. This exercise revealed several shortcomings of the bioreactor equipment which required the development of alternative methodology. The most significant of these was that the oxygen measurement channel of the exit gas analyser functioned incorrectly, and this apparatus could therefore not be used for online growth estimation.

An alternative method for measuring oxygen uptake was developed that involved the use of the reactor dissolved oxygen probe. This was demonstrated to have reasonable functionality during bioreactor runs but suffered limitations, and the repair or replacement of the gas analyser is a principal recommendation of this thesis.

Model parameterisation using the bioreactor was attempted using both continuous and fed-batch culture methods. For the former, contamination of the feed reservoir resulted in abandonment of the experiment and the method was not repeated due to cost and time constraints. The fed-batch experiments were also unsuccessful, and the factors responsible were determined to be related to growth medium composition and the secondary metabolic pathways inherent to the yeast.

Despite incompletion of the second objective, the project highlighted several key issues related to bioreactor monitoring and control, yeast metabolism and experimental design. The Murdoch bioreactor was demonstrated to be suitable for the three primary modes of bioreactor operation, namely batch, fed-batch and continuous culture, although modifications to methodology are required for successful modelling applications of these. Numerous recommendations for the improvement of bioreactor operation have been made, and several potential future projects have been identified.

Item Type: Thesis (Other)
Murdoch Affiliation(s): School of Engineering and Information Technology
Supervisor(s): Vu, Linh
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