(190e) Physiological, Molecular, and in Silico Analysis of Lipid Accumulation in the Marine Diatom Phaeodactylum Tricornutum

Photosynthesis derived lipids are considered promising precursors for sustainable biodiesel production. A detailed physiological, molecular, and in silico analysis of lipid accumulation under a suite of conditions including nitrogen limitation, alkaline pH stress, bicarbonate supplementation and organic acid supplementation was performed on the marine diatom Phaeodactylum tricornutum. For all tested conditions, nitrogen limitation was a prerequisite for lipid accumulation and the other culturing strategies only enhanced accumulation highlighting the importance of compounded stresses on lipid metabolism. Volumetric lipid levels varied depending on condition; the observed rankings from highest to lowest were for inorganic carbon addition (15 mM bicarbonate), organic acid addition (15 carbon mM acetate) and alkaline pH stress (pH 9.0). The results were incorporated into a genome-enabled stoichiometric model of the central metabolism of this diatom.  Analysis suggested the central metabolism pathways associated with bicarbonate transport, carbonic anhydrases and C4 carbon fixation were important for lipid accumulation. Transcriptomic data also suggested that repurposing of phospholipids may play a role in lipid accumulation. This study provides a detailed physiological, molecular-level, and in silico foundation for improved understanding of diatom nutrient cycling and contributes to a metabolic blueprint for controlling lipid accumulation in diatoms.