Description of a new species of soil algae, Parietochloris grandis sp. nov., and study of its fatty acid profiles under different culturing conditions

The new species Parietochloris grandis sp. nov. is described from forest soil in the Dnipropetrovsk region, Ukraine. The description is based on morphological features and the phylogenetic analysis of partial SSU rDNA and rbcL genes. Phylogenetic analysis places P. grandis in the Parietochloris clade, within the family Trebouxiophyceae. The novel strain formed a strongly supported monophyletic lineage with the type species of Parietochloris, P. alveolaris. P. grandis differed from other species in the Parietochloris clade by the size and form of vegetative cells and the large number of zoospores in zoosporangia. A number of experiments with different phosphates and nitrates concentrations were conducted to evaluate changes in fatty acid profile and biomass. The dominant fatty acids during cultivation on standard BG-11 medium, as well as with the phosphates concentrations ranged from 0.22 to 2 mM, were linoleic acid (24-25%), palmitic acid (12-14%), linolenic acid (9-12%), and oleic acid (7-11%). The content of arachidonic acid and eicosapentaenoic acid ranged from 3.5 to 4.5% and 0.7% to 0.8%, respectively. The fatty acid profile and total fatty acids varied significantly under different nutrient deficiency. The greatest variation was found for oleic acid (9-46%) and linolenic acid (2-13%). The percentage of arachidonic acid was the highest with a standard nitrates concentration in the medium (5%) and the lowest in the absence of phosphates and nitrates (1.3-1.5%), but the absolute content in dry biomass was similar in all variants of the experiment (6.5-9.3 mg g−1 dry weight). The absence of nitrogen and both nitrogen and phosphorus led to a 3-fold increase in TFA in comparison with the control. Thus, this strain can be considered in biotechnological application as a potential producer of the essential linoleic acid or oleic acid.