Effects of nitrogen starvation on protein and carbohydrate contents of some marine microalgae and their efficiency as food for the rotifer Brachionus plicatilis (Müller)

The utilization of microalgae biomass shows vast invaluable uses, in the biotechnology of aquaculture, and food science. However, microalgae exhibit swing in their chemical components created mainly by the culture of different conditions. This study considers the impact of nitrogen starvation on protein and carbohydrate of Nannochloropsis salina, Nannochloropsis oculata, Chlorella salina and Tetraselmis chuii, and the sub­sequent effects of the previously mentioned microalgae on the fatty acid composition (FA) of the rotifer Brachionus plicatilis. Cultivation of microalgae was cultured with F/2 enriched seawater medium (control) and without nitrogen (N starved) in 8-day (exponential growth phase). The result indicated that N. salina is the best algal species, and have higher protein contents (41.88 ± 1.40 µg/ml) cultured on N starved media against control, followed by T. chuii, otherwise, T. chuii have higher carbohydrate contents. The lipid classes and FA composition of B. plicatilis showed higher concentrations (450.63 μg.g^-1) with N. salina cultured on N starved media, in parallel, total (n-3) PUFA were recorded (57.19 μg.g^-1), while, total (n-6) PUFA amounted (23.74 μg.g^-1). On the other hand, DHA/EPA ratio was higher when rotifers were fed on T. chuii. The results confirmed that N. salina was the excellent producing protein which significantly could be used as a fish feed product. Moreover, the proximate analysis of rotifers was influenced by the type of microalgae they utilized.