Development of microalgae tools and techniques: Metabolic engineering of lipid profiles

摘要

Microalgae are drawing increased attention from a variety of fields ranging from nutrition and health care to energy, and deservedly so. The potential of algae is almost unparalleled as a biomanufacturing platform. Microalgae can be used to produce complex human antibodies to target cancerous cells, or as crops for the production of high quality food, or even as sources of lipids for conversion into biofuels. They can grow to tremendous density in bioreactors, or be cultivated in open ponds where their yield per acre dominates that of higher plants.;Research in microalgae needs to take it to the next step, to transform potential into reality and make production strains of microalgae into designer products that are custom tailored to suit the needs of the industry. The diversity of microalgae is enormous, and as a result, it is unlikely that the strains we have identified today will be the same we see as ideal production strains tomorrow. So in order to continue advancing the field, techniques for ideal cultivation, genetic modification, and metabolic engineering will need to be developed. This thesis work seeks to do just that by covering cultivation technology, metabolic engineering of lipids, and genetic modification of potential production strains.;From a molecular perspective, a broad review of the current state of lipid metabolic engineering in both microalgae and higher plants is provided, covering both the biofuel relevant molecules as well as nutritionally relevant omega-3 fatty acids. New techniques for rapid interrogation of protein, lipid, and dry weight content in microalgae under either indoor or outdoor cultivation techniques are also described herein. These will enable more efficient harvesting and culturing techniques as well as more efficient use of fertilizers and nutrients in cultivation of microalgae. Proof of concept for custom tailoring lipid profile is demonstrated in the manipulation of Chlamydomonas reinhardtii lipid metabolism for the production of very long chain polyunsaturated fatty acids, which also provides insights into how changes in lipid profile can have unexpected effects and yield new insights on lipid metabolism. Finally, attempts to characterize and transform a variety of potential production species are covered and reveal challenges to the transformation of new microalgae species. Taken together, this work represents significant advances in the field with regard to both cultivation and transformation and metabolic engineering of microalgal species.