Influence of nitrogen and phosphorus stress on growth and fatty acids of the microalgae Vischeria calaminaris (Eustigmatophyceae)

The effect of nitrogen and phosphorus stress on the growth and fatty acid profile of the eustigmatophycean alga Vischeria calaminaris (Trzcinska et Pawlik-Skowronska) Kryvenda, Rybalka, Wolf et Friedl was studied. The strain MZ–E6 isolated from the soil of a black locust plantation is the first find of Vischeria calaminaris in the territory of European Russia. Taxonomic identification was carried out based on morphological analysis and phylogenetic reconstruction using nucleotide sequences of the 18S rRNA gene. The experiment used a stepwise change in the concentrations of nitrogen (from 0 to 0.6 g/l) and phosphorus (from 0 to 0.3 g/l) in the BBM medium. Cultivation of the MZ‒E6 strain for 20 days demonstrated accumulation of dry biomass in the range of 3.36–4.48 g/l with the maximum value under moderate limitation of nitrogen content (0.15 g/l). In all experimental variants, the dominant fatty acids were palmitic, palmitoleic, oleic and eicosapentaenoic, accounting for 84.67–87.02% of the total fatty acids. It was found that phosphorus stress leads to more significant changes in the fatty acid composition compared to nitrogen stress. It has been shown that an effective strategy is to cultivate the Vischeria calaminaris MZ–E6 strain on BBM medium with a nitrogen concentration of 0.2 g/l and phosphorus of 0.11 g/l: this allows obtaining sufficient amounts of biomass (4.19 g/l) with a high content of saturated and polyunsaturated fatty acids (more than 66% in total).