Effects of Nitrogen Starvation on Growth and Biochemical Composition of Some Microalgae Species

Abstract

AbstractNitrogen is one of the most important nutrient sources for the growth of microalgae. We studied the effects of nitrogen starvation on the growth responses, biochemical composition and fatty acid profile ofDunaliella tertiolecta, Phaeodactylum tricornutumandNannochloropsis oculata. The lack of nitrogen caused changes in carbohydrate, protein, lipid and fatty acid composition in all examined microalgae. The carbohydrate content increased 59% inD. tertiolecta, while the lipid level increased 139% inP. tricornutumunder nitrogen stress conditions. Nitrogen starvation increased the oligosaccharide and polysaccharide contents ofD. tertiolecta4.18-fold and 3.77-fold, respectively. Furthermore, triacylglycerol (TAG) levels inN. oculataandP. tricornutumincreased 2.3-fold and 7.4-fold, respectively. The dramatic increase in the amount of TAG is important for the use of these microalgae as raw materials in biodiesel. Nitrogen starvation increased the amounts of oligosaccharides and polysaccharides ofD. tertiolecta, while increased eicosapentaenoic acid (EPA) inN. oculataand docosahexaenoic acid (DHA) content inP. tricornutum. The amount of polyunsaturated fatty acids (PUFAs), EPA, DHA, oligosaccharides and polysaccharides in microalgal species can be increased without using the too costly nitrogen source in the culture conditions, which can reduce the most costly of living feeding.