Identification of fatty acid biomarkers for quantification of neutral lipids in marine microalgae Isochrysis zhangjiangensis

Fatty acid biomarkers of the marine microalga Isochrysis zhangjiangensis in response to nitrogen depletion were identified by multivariate statistical analysis. Seven fatty acids (C16:0, C18:1n9, C18:4n3, C18:3n3, C18:5n3, C22:6n3, and C16:1n7) were selected and identified as potential biomarkers, among which C18:1n9 and C18:4n3 were enriched in the neutral lipids and glycolipids, respectively. Due to significant changes and specific distributions in different types of lipids, C18:1n9 and C18:4n3 were identified as biomarkers to quantify neutral lipid content. C18:1n9 was positively related with neutral lipid content, while C18:4n3 was negatively related with neutral lipid content. The correlation coefficients of C18:1n9 and C18:4n3 content in total fatty acids and neutral lipid content were 0.9960 and 0.9787, respectively. The good agreement between the neutral lipids content and fatty acid biomarkers content in total fatty acids indicates that neutral lipids can be quantified by specific fatty acids. Using fatty acid biomarkers to quantify neutral lipids requires much less sample analyzed by gas chromatography, which is a universal method, plus the simplicity of operation compared with conventional methods. The striking feature of the approach is individual fatty acid to represent the type of lipids. Therefore, applying fatty acid biomarkers to identify specific type of lipids promises to maximize lipid-related information and can be used to make further discoveries related to lipid metabolism.