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Biological stoichiometry of oleaginous microalgal lipid synthesis: The role of N:P supply ratios and growth rate on microalgal elemental and biochemical composition
- Gao, Baoyan, Liu, Jing, Zhang, Chengwu, Van de Waal, Dedmer B.
- Algal research 2018 v.32 pp. 353-361
- Tetradesmus, carbon nitrogen ratio, glycolipids, lipid content, microalgae, nitrogen content, phospholipids, protein content, stoichiometry, triacylglycerols
- Biological Stoichiometry is an ecological framework connecting the balance of elements to the functioning of organisms. Here, we applied this framework to study the relationships between carbon:nitrogen:phosphorus (C:N:P) ratios and synthesis of industrial high value biochemicals in the highly oleaginous alga Tetradesmus bernardii. We expected an increase in protein content with increasing cellular N content and decreasing C:N stoichiometry, and an increase in lipid content with increasing C:N and C:P stoichiometry. We tested these hypotheses by exposing T. bernardii to N and P limitation at a range of N:P supply ratios in chemostats set at low and high dilution rates. Following expectations, the cellular protein content increased with the N content, and decreased with cellular C:N ratios across all treatments. Carbohydrates and lipids largely followed the relative availability of C and increased under both N and P limitation, with higher C:N and C:P ratios. Specifically, lipid content increased by 100–125% upon N and P limitation, with a shift towards more neutral lipids at the cost of glycolipids and phospholipids. Generally, we observed a re-allocation of cellular C from protein to carbohydrates upon modest N limitation, and towards lipids under P and severe N limitation. Our results demonstrate stoichiometrically predictable patterns of industrially valuable compounds in an oleaginous microalga.