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Item Control of triacylglycerol accumulation and bicarbonate-induced accumulation in microalgae(Montana State University - Bozeman, College of Engineering, 2012) Gardner, Robert David; Co-chairpersons, Graduate Committee: Brent M. Peyton and Keith Cooksey; Patrizia Peters, Brent M. Peyton, and Keith E. Cooksey were co-authors of the article, 'Medium pH and nitrate concentration effects on accumulation of triacylglycerol in two members of the chlorophyta' in the journal 'Journal of applied phycology' which is contained within this thesis.; Robert D. Gardner, Keith E. Cooksey, Florence Mus, Richard Macur, Karen Moll, Everett Eustance, Ross P. Carlson, Robin Gerlach, Matthew W. Fields, and Brent M. Peyton were co-authors of the article, 'Use of sodium bicarbonate to stimulate triacylglycerol accumulation in the chlorophyte scenedesmus sp. and the diatom phaeodactylum tricornutum' in the journal 'Journal of applied phycology' which is contained within this thesis.; Egan Lohman, Robin Gerlach, Keith E. Cooksey and Brent M. Peyton were co-authors of the article, 'Comparison of CO 2 and bicarbonate as inorganic carbon sources for triacylglycerol and starch accumulation in Chlamydomonas reinhardtii' in the journal 'Biotechnology and bioengineering' which is contained within this thesis.Microalgae are capable of accumulating high levels of lipids and starch as carbon storage compounds. Investigation into the metabolic activities involved in the synthesis of these compounds has escalated since these compounds can be used as precursors for food and fuel. This dissertation represents the summary of work completed to evaluate factors that control and stimulate triacylglycerol (TAG) accumulation in microalgae, and demonstrate the use of sodium bicarbonate as a chemical additive to induce TAG accumulation. Two Chlorophytes, Scenedesmus sp. WC-1 and Coelastrella sp. PC-3, were analyzed in pH buffered systems to determine the effect of pH on growth and TAG accumulation, both with and without nitrate deplete conditions. Medium nitrate and pH were found to be independent stress mechanisms and the causal effects of each were determined. Growth and TAG accumulation was optimized on the Chlorophyte Scenedesmus sp. WC-1 and the addition of bicarbonate was shown to arrest cellular replication and induce an elevated TAG accumulation rate. Thus, decreasing the total culturing time required for TAG production by half. To ascertain whether the addition of bicarbonate would give similar results in other algae, the marine diatom Phaeodactylum tricornutum Pt-1 and the model Chlorophyte Chlamydomonas reinhardtii were evaluated similar to WC-1. C. reinhardtii showed a cessation of the cell cycle with bicarbonate addition while P. tricornutum Pt-1 did not. However, the addition of bicarbonate was shown to induce lipid accumulation in both organisms. This demonstrates the broad use of bicarbonate as a means of inducing TAG accumulation in microalgae (Chlorophytes and diatoms, freshwater or marine).