Date of Award
Doctor of Philosophy (PhD)
Concerns over the impact of climate change caused by CO2 emission have driven the research and development of renewable energies. Microbial production of chemicals is being viewed as a feasible approach to reduce the use of fossil fuels and minimize the impact of climate change. With recent advances in synthetic biology, microorganisms can be engineered to synthesize petroleum-based chemicals and plant-derived compounds. Cyanobacteria are photosynthetic prokaryotes that use only sunlight, CO2, and trace minerals for growth. Compared to other microbial hosts, cyanobacteria are attractive platforms for sustainable bioproduction, because they can directly convert CO2 into products. However, the major challenge of using cyanobacteria for chemical production is their low productivities compared to that of conventional heterotrophic hosts. More research is needed to improve the photosynthetic conversion of CO2 to desired compounds. In this dissertation, cyanobacteria were engineered to produce two commercially-used products, limonene and sucrose, which use distinct substrates for biosynthesis. To identify the metabolic bottlenecks for enhancing the production of limonene and sucrose, various genes and pathways were expressed in cyanobacteria, and further optimized using synthetic biology tools. Their productivities were significantly improved compared to those reported in previous studies. The findings in this dissertation provide knowledge to improve cyanobacterial production of limonene and sucrose, and facilitate a deeper understanding of the terpene and sugar metabolism in these photosynthetic microorganisms.
Fuzhong Zhang, Costas Maranas, Tae Seok Moon, Yinjie Tang,