Metabolic Profiling of Dunaliella salina Shifting Cultivation Conditions to Nitrogen Deprivation

Abstract

Dunaliella salina is a model chlorophyte microalga in studying carotenoid metabolism and osmoregulation. Nitrogen depletion plays an important role in inducing β-carotene accumulation of D. salina cells. However, the underlying mechanism is still unclear. In this study, the metabolic profiling of D. salina cells during the process of nitrogen deprivation was performed by gas chromatography-mass spectrometry. A total of 78 metabolites were identified and quantified, including 16 amino acids, 19 sugars, 13 organic acids, 11 alcohols, 11 fatty acids, 4 amines and 4 others. Nitrogen deprivation induced changes in saturation of fatty acids by increasing saturated fatty acids and decreasing polyunsaturated fatty acids in D. salina. The relative levels of metabolites such as sucrose, maltose and organic acids, which act as carbon skeleton, were increased, in contrast, glycerol, myo-inositol which are related to the osmoregulatory mechanism, kept constant under nitrogen deprivation condition. The levels of proline, glutamic acid and other metabolites, which were involved in protective function, were increased in nitrogen deprivation condition. The precursors of these metabolites are the intermediates of the Calvin cycle and the TCA cycle. The results of this research might be applicable to the interpretation of metabolic synthesis and fatty acid production during process of nitrogen deprivation and provide a new method for accumulating high amounts of carotenoids in D. salina.