Abstract
Microalgae represent a third generation biofuel feedstock due to their high triacylglycerol (TAG) content under adverse environmental conditions. Microalgal TAG resides in a single cell and serves as a lipid class mixed with complicated compositions. We previously showed that TAG possessed characteristic fatty acids (CFAs) for quantification and was linearly correlated with the relative abundance of CFA within certain limits in microalgae. Here, we defined the application range of the linear correlation between TAG and CFA in the oleaginous microalgae Chlamydomonas reinhardtii and Phaeodactylum tricornutum. In addition, TAG quantification was further expanded to a wide range of levels and the absolute amounts of saturated or monounsaturated CFAs, 16:0 and 18:1n9 of C. reinhardtii and 16:0 and 16:1n7 of P. tricornutum, instead of polyunsaturated CFAs, were verified to be linearly correlated to TAG levels throughout the entire period of nitrogen stress. This approach utilizes a single fatty acid to quantify TAG mixtures, and is rapid, simple and precise, which provides a useful tool for monitoring TAG accumulation of distinct microalgal species and facilitating high-throughput mutant screening for microalgae.
Highlights
Microalgae have emerged as a promising renewable resource for producing triacylglycerols (TAGs), which can be used as biofuel feedstocks (Wijffels and Barbosa, 2010)
In P. tricornutum, both 16:0 and 16:1n7 rose up to 1.6-fold of the initial levels and 16:3n4 and EPA sharply declined to 20 and 30% after 72 h of N-depletion, respectively. These two microalgae accumulated TAGs up to 17% for C. reinhardtii and 20% for P. tricornutum based on dry weight (DW) (Figures 2A,B)
During Stage II, the relative fatty acid percentages of these two algae were almost unaltered; TAG substantially accumulated up to 43% for C. reinhardtii and 32% for P. tricornutum based on DW (Figures 2A,B)
Summary
Microalgae have emerged as a promising renewable resource for producing triacylglycerols (TAGs), which can be used as biofuel feedstocks (Wijffels and Barbosa, 2010). Nitrogen starvation is the most effective manner to induce microalgal TAG biosynthesis (Zienkiewicz et al, 2016). It is necessary to investigate performance of TAG accumulation under distinct levels of nitrogen stress in microalgae to screen potential candidates for oleaginous species. Microalgae are different from other oleaginous feedstocks, such as plant seeds, of which the lipids are dominated by TAG. Microalgae exist in form of a single cell and contain various lipids with different polarities. The chloroplast serves as the largest organelle and contains many complicated and hydrophobic components, which makes TAG quantification more intricate. It is desirable to develop an approach to efficiently quantify TAG content of microalgal biomass under various growth conditions
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