Positional distribution of fatty acids in triacylglycerols of the microalga Vischeria punctata IPPAS H-242 reveals their high nutraceutical potential

The positional distribution of fatty acids (FAs) in Vischeria punctata strain IPPAS H-242 during nitrogen starvation was analysed, and 22 individual FAs were identified in total lipids, TAGs, and native sn-1,2-diacylglycerols, comprising both saturated and polyunsaturated FAs. The predominant FAs were 14:0, 16:0, 16:1n-7, 18:1n-9, and 20:5n-3, accounting for more than 98.5% of the total FAs. TAGs demonstrated unique regioselectivity, with stearic, oleic, and eicosapentaenoic acids acylating the molecules at sn-1 and sn-3 positions. Instead, the sn-2 position was acylated with myristic, palmitic (8.4% and 40.1%, respectively) and palmitoleic (50.6%) acids, resulting in a total contribution of 99.1% from these three FAs. Palmitic, palmitoleic, and oleic acids made up 7.5, 73.9, and 13.1% of the sn-1(3) positions, respectively, or 94.5% in total. The molecular types of TAGs that accumulated in the cells of the microalga Vischeria punctata were as follows: UUU, 41.3%, and USU, 39.2%; TAGs of the UUS and USS types accounted for 9.4% and 9.0%, respectively. Tripalmitoleoyl-triacylglycerol, sn-1,3-dipalmitoleoyl-2-palmitoyl-glycerol, rac-1-oleoyl-2,3-dipalmitoleoyl-glycerol, and rac-1-oleoyl-2-palmitoyl-3-palmitoleoyl-glycerol were found as the most common molecular species of TAGs. Thus, Vischeria punctata strain IPPAS H-242 may be considered as a potential producer of structured TAGs with palmitic acid at the sn-2 position and palmitoleic acid at the sn-1 and sn-3 positions. The subsequent hydrolysis of such TAGs by pancreatic lipase produces palmitoleic acid and sn-2-palmitoylglycerol that have significant nutraceutical value and serve as a source of digestible palmitic acid for infant nutrition.