## 3 Results and Discussion
### Synthesis of Storage Lipids and Fatty Acid Composition of Total Lipids and Lipid Fractions
Moreover, PUFAs are of great commercial interest for the food, animal feed, and pharmaceutical industries, as they present beneficial effects against various threats to human and animal health, like cardiovascular and neurodegenerative diseases, while other studies have investigated their potential as anticancer agents with promising results [53; 54; 55; 56]. In any case, several studies have concluded that glycolipid content could be increased under conditions of nitrogen or phosphorus deficiency [57; 58; 59]. In contrast, the dominant lipid fraction of _N. pyriformis_ PAT2.7 was the NL fraction (i.e., 50.1 \(\pm\) 0.4%, wt/wt), which represents mainly storage lipids, followed by the G+S fraction (i.e., 43.6 \(\pm\) 0.7%, wt/wt). Some microalgae alter their lipid biosynthetic pathways towards the synthesis of more neutral lipids under stress conditions, as has occurred for _Scenedensmus_ sp. (Chlorophyta), _Isochrysis galbana_ (Coccolithophyceaeae), and _Diacronema lutheri_ (formerly known as _Pavlova lutheri_) (Pavlovophyceae) under phosphorus limitation [60; 61]. Moreover, in general, low light intensities favor polar lipid synthesis, while the opposite occurs under high light intensities [60]. Thus, it might be an indication that, herein, the supplied illumination for _N. pyriformis_ PAT2.7 was relatively high. As mentioned previously, though, during the growth cycle, lipid content varies in quantity and quality as well. For example, during the stationary phase, as happened for the harvested biomass of _N. pyriformis_ PAT2.7 in this study, an increased TAG level is often observed [45]. The composition of total lipids and their lipid fractions in fatty acids at the end of the cultures of the four microalgal strains are presented in Table 3.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Strain**} & \multicolumn{4}{c}{**Lipid**} & \multicolumn{6}{c}{**Compression of Total Lipids and Lipid Fractions in Fatty Acids (\%, wt wt wt)**} \\ \cline{3-14}  & **Fraction** & **Clalo** & **\#C14** & **Clalo** & **\#C16** & **\#C18** & **\#C18** & **\#C18** & **\#C18** & **\#C18** & **\#  
Regarding _P. costavermella_ VAS2.5, the predominant fatty acid in TL is \({}^{\Delta 9}\)C16:1 (27.9 \(\pm\) 0.5%, wt/wt), followed by a significant amount of \({}^{\Delta 5,8,11,14,17}\)C20:5 (23.4 \(\pm\) 3.9%, wt/wt) and C16:0 (15.7 \(\pm\) 0.1%, wt/wt). As shown in Table 3, \({}^{\Delta 9,12}\)C18:2 was almost consumed, while \({}^{\Delta 9,12,15}\)C18:3 was not detected. This is likely due to the activity of \(\Delta 6\) and \(\Delta 5\) desaturases and \(\Delta 6\) elongates that led to the production of \({}^{\Delta 5,8,11,14,17}\)C20:5 in significant amounts [1]. The NL lipid fraction showed a similar pattern to that of TL, except for the percentage of \({}^{\Delta 5,8,11,14,17}\)C20:5, which was about half (10.0 \(\pm\) 2.5%, wt/wt), whereas the percentage of \({}^{\Delta 9}\)C18:1 was higher (i.e., 14.7 \(\pm\) 3.9%, wt/wt against 6.6 \(\pm\) 0.0, wt/wt, in TL). Similar composition and content to TL were noted for the lipid fractions G and P, with the difference of a higher percentage of \({}^{\Delta 5,8,11,14,17}\)C20:5 (31.1 \(\pm\) 0.9%, wt/wt) in the P fraction. In the case of _P. oklahonense_ SAG4.4, the fatty acid \({}^{\Delta 9,12}\)C18:2 was the dominant one in TL (i.e., 29.6 \(\pm\) 2.0%, wt/wt), followed by significant amounts of \({}^{\Delta 9,12,15}\)C18:3 (16.6 \(\pm\) 0.6%, wt/wt), C16:0 (14.8 \(\pm\) 0.0%, wt/wt), and \({}^{\Delta 9}\)C18:1 (13.8 \(\pm\) 1.4%, wt/wt). Intriguingly, in this _Picochlororum_ strain, it seems that lipid biosynthesis practically was terminated in \({}^{\Delta 9,12,15}\)C18:3, which can be considered as an indication of the absence of activity regarding \(\Delta 6\), \(\Delta 5\) desaturases, and \(\Delta 6\) elongase [1].