The role of low oxygen microenvironments in microbial polyhydroxyalkanoate production using Pseudomonas putida and application to bioreactor operations for improved productivity
| dc.contributor.author | Blunt, Warren | |
| dc.contributor.examiningcommittee | Levin, David (Biosystems Engineering) Gapes, Daniel (Biosystems Engineering) Sparling, Richard (Microbiology) Pratt, Steven (Chemical Engineering, The University of Queensland) | en_US |
| dc.contributor.supervisor | Cicek, Nazim (Biosystems Engineering) | en_US |
| dc.date.accessioned | 2019-10-02T14:20:12Z | |
| dc.date.available | 2019-10-02T14:20:12Z | |
| dc.date.issued | 2019 | en_US |
| dc.date.submitted | 2019-06-26T20:21:56Z | en |
| dc.degree.discipline | Biosystems Engineering | en_US |
| dc.degree.level | Doctor of Philosophy (Ph.D.) | en_US |
| dc.description.abstract | Synthesis of medium chain-length polyhydroxyalkanoates (mcl-PHAs) is an oxygen-requiring process. Maintaining an adequate supply of dissolved oxygen (DO) is a significant engineering challenge, and can be costly in large-scale bioreactors. The objective of this work was to understand the effect(s) that low-DO environments have on mcl-PHA synthesis in Pseudomonas putida LS46. This work focuses on two main aspects: 1) investigating fundamental physiology in microaerophilic environments; and 2) understanding how the findings could be applied to process design for bioreactor operations. In the first aspect, low-DO environments were studied in lab-scale bioreactors, mimicking conditions that might be encountered in large-scale vessels. At low DO, carbon flux to mcl-PHA exhibited considerable dependence on the carbon substrate and hence the biochemical pathway used for mcl-PHA biosynthesis. It was found that significant mcl-PHA was synthesized from β-oxidation intermediates (an oxidative process), but not when precursor monomers were obtained via a de novo fatty acid biosynthetic pathway (a reductive process). In the latter case, most of the carbon was respired as CO2. For substrates that use both pathways to some degree, low DO increased the content of monomers incorporated from β-oxidation intermediates. In the second aspect of this work, an O2-limited high-cell density fed-batch strategy was developed and implemented for improved productivity, and the effects of culture rheology on process performance were assessed. Finally, a lab-scale semi-continuous sequencing-batch system was pursued to investigate long-term performance in a non-sterile environment. It was found that fatty acid carbon substrates were highly selective for mcl-PHA producing organisms, such that the productivity of this system was comparable to a similar process in a sterile environment. iii Collectively, this work represents the most comprehensive study available on the effects of O2-limitation in mcl-PHA synthesis. The findings improve fundamental understanding of how P. putida LS46 metabolism responds to its environment and also have implications for process design, including: 1) under what conditions low-DO environments can benefit mcl-PHA synthesis; 2) possibilities for co-feeding substrates to improve residual growth or PHA yield; 3) how DO might alter monomer compositions; and 4) process configurations that can improve productivity under microaerophilic conditions. | en_US |
| dc.description.note | October 2019 | en_US |
| dc.identifier.citation | Blunt, Warren, Christopher Dartiailh, Richard Sparling, Daniel Gapes, David B. Levin, and Nazim Cicek. "Microaerophilic environments improve the productivity of medium chain length polyhydroxyalkanoate biosynthesis from fatty acids in Pseudomonas putida LS46." Process Biochemistry 59 (2017): 18-25. | en_US |
| dc.identifier.citation | Blunt, Warren, Christopher Dartiailh, Richard Sparling, Daniel Gapes, David B. Levin, and Nazim Cicek. "Carbon flux to growth or polyhydroxyalkanoate synthesis under microaerophilic conditions is affected by fatty acid chain-length in Pseudomonas putida LS46." Applied microbiology and biotechnology 102, no. 15 (2018): 6437-6449. | en_US |
| dc.identifier.citation | Blunt, Warren, Richard Sparling, Daniel J. Gapes, David B. Levin, and Nazim Cicek. "The role of dissolved oxygen content as a modulator of microbial polyhydroxyalkanoate synthesis." World Journal of Microbiology and Biotechnology34, no. 8 (2018): 106. | en_US |
| dc.identifier.citation | Blunt, Warren, David Levin, and Nazim Cicek. "Bioreactor operating strategies for improved polyhydroxyalkanoate (pha) productivity." Polymers 10, no. 11 (2018): 1197. | en_US |
| dc.identifier.citation | Blunt, Warren, Alain Lagassé, Zimo Jin, Christopher Dartiailh, Richard Sparling, Daniel J. Gapes, David B. Levin, and Nazim Cicek. "Efficacy of medium chain-length polyhydroxyalkanoate biosynthesis from different biochemical pathways under oxygen-limited conditions using Pseudomonas putida LS46." Process Biochemistry 82 (2019): 19-31. | en_US |
| dc.identifier.uri | http://hdl.handle.net/1993/34318 | |
| dc.language.iso | eng | en_US |
| dc.rights | open access | en_US |
| dc.subject | Polyhydroxyalkanoates | en_US |
| dc.subject | Pseudomonas putida | en_US |
| dc.subject | Dissolved oxygen | en_US |
| dc.subject | Bioreactor | en_US |
| dc.subject | Biopolymer | en_US |
| dc.subject | Mass transfer | en_US |
| dc.title | The role of low oxygen microenvironments in microbial polyhydroxyalkanoate production using Pseudomonas putida and application to bioreactor operations for improved productivity | en_US |
| dc.type | doctoral thesis | en_US |