Production and detection of polyhydroxybutyrate (PHB) in the alphaproteobacterial methanotroph Methylocystis sp. Rockwell

• Author / Creator

  Lazic, Marina

• Anthropogenic agricultural and industrial activities have intensified in the past few decades to satisfy the food and energy demands of a rapidly growing human population. The increase in these activities is causing extremely high emission of greenhouse gases which results in global warming and inevitable climate change. One of the most potent greenhouse gases is methane. From a biological perspective, methane represents a sole carbon source for microorganisms known as methanotrophs. These microbes, which are the only known biotic methane sink, can act as natural barrier to methane emissions. From an industrial perspective, these organisms can be used as microbial factories to produce value-added compounds from methane. Another important feature of methanotrophs is their ability to consume methanol as well as methane, which is immediately available without the need to control gas to liquid mass transfer.
  The focus of this thesis is the alphaproteobacterial methanotroph Methylocystis sp. Rockwell. Alphaproteobacterial methanotrophs encode the enzymatic machinery for the production of bioplastics while growing on methane and/or methanol. The most important bioplastic produced by alphaproteobacterial methanotrophs is polyhydroxybutyrate (PHB). The overall goal of this study was to optimize production and detection of PHB in Methylocystis sp. Rockwell.
  To optimize production of PHB, bacterial cultures were grown under different combinations of methane and/or methanol with ammonium or nitrate mineral salts as the source of nitrogen. Growth was monitored along with oxygen and methane consumption, while biomass and PHB were analyzed at the end of growth. Results of this study revealed the importance of methane/methanol combination for PHB production, regardless of nitrogen

  source, and led to the question of the mechanism of beneficial influence of methanol on PHB synthesis.
  In addition, this study established novel, environmentally friendly, cheaper, and faster approach for direct PHB detection in methanotroph cells and confirmed its accuracy with the standard detection approach. In another approach, a molecular tool for detection of novel PHB-producing organisms in the environment was created, and the proof-of-concept principle has been confirmed.
  Overall, results of this study offer new perspectives in both, optimization and detection/quantification and serve as the basis for further improvements in designing methanotrophic PHB biofactories.

• Subjects / Keywords

  • methanotrophs
  • methane
  • methanol
  • polyhydroxybutyrate
  • Methylocystis sp. Rockwell

• Graduation date

  Spring 2023

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-bpt3-p320

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.