The Synthetic Biology of N2-Fixing Cyanobacteria for Photosynthetic Terpenoid Production

<p>In the last few decades, concerns over global climate change, energy security, and environmental pollution have been rising. To overcome these challenges, the concept of “-n^th generation” biofuels has emerged as a strategy to convert solar radiation into fuels and bulk industrial chemicals for societal use, while decreasing our consumption of nonrenewable energy sources. Nitrogen-fixing cyanobacteria hold a distinct advantage in biofuel production over plants, given their ability to convert sunlight, air (CO₂ and N₂), and mineralized water to energy-dense carbon molecules, as well as fix atmospheric nitrogen gas into ammonia for metabolism. Engineered cyanobacteria with re-wired metabolic pathways have recently been designed through synthetic biology, and they possess the ability to synthesize new chemicals and biofuels, which are secreted from their cells. Terpenoids constitute one of the largest classes of organic molecules on Earth, and are attractive candidates as a fourth generation biofuel and industrial chemical. In cyanobacteria, the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway is responsible for building essential metabolites involved in photosynthesis, as well as precursors for terpenoid biosynthesis. This dissertation encompasses research focused on redirecting MEP flux in the nitrogen-fixing cyanobacterium <em>Anabaena</em> sp. PCC 7120 to engineered terpenoid sinks, namely, linalool (C₁₀H₁₈O) and farnesene (C₁₅H₂₄). Chapter 1 is a review of literature in the field of biofuels and cyanobacteria, and chapter 2 is an introduction/list of objectives for the research in this dissertation. In chapter 3, we present the genetic engineering of <em>Anabaena</em> to synthesize farnesene by expressing a plant farnesene synthase. In chapter 4, we present the genetic engineering of <em>Anabaena</em> to synthesize linalool during N₂-fixation, and increased linalool production is accomplished by the over-expression of three ratelimiting enzymes in the MEP pathway. In chapter 5, we examine the feasibility of a blocking a native carbon reservoir in the cyanobacterium to increase metabolite and energy availability for terpenoid synthesis, as well as physiological aspects of glycogendeficiency in the cyanobacterium during diazotrophic growth. In chapter 6, we focus on introducing a synthetic photorespiratory bypass to reduce photorespiration and increase carbon partitioning towards linalool synthesis.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation - Open Access

Discipline thesis:degree_discipline

Biology and Microbiology

Year dc:date.available

2017

Author dc:creator

• Halfmann, Charles T.

Contributors dc:contributor

• Ruanbao Zhou

• biofuel
• cyanobacteria
• farnesene
• linalool terpenoids
• Bioresource and Agricultural Engineering
• Microbiology
• Molecular Biology

Licence

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language

en

Repository record dc:identifier

https://openprairie.sdstate.edu/etd/1213

OAI identifier oai:identifier

oai:openprairie.sdstate.edu:etd-2220