## 3 Results and Discussion
### Fatty Acid Methyl Esters Analysis (FAMEs)

Table 3: Fatty acid (FA) composition (mass% of total FA identified) analyzed by GC with Flame-Ionization Detection (GC-FID) of _P. tricornutum_ culture under different conditions (white light (W), red light (R), or red light shift (RS)). Data are expressed as the mean of three independent experiments. and R induced the production of monounsaturated fatty acids as compared to RS. The total percent of saturation and unsaturation--especially the amount of long-chain polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)--will have an impact on the biodiesel fuel properties [60]. The results showed that the cetane number (CN), which determines the ignition quality of the fuel, is higher in _P. tricornutum_ cultured in R and RS as compared to W (Table 5). It is known that the higher the CN, the better the ignition of the fuel and vice versa [57]. Literature studies have also mentioned that increases in the degree of unsaturation lead to decreases in CN viscosity, which is a useful measure for monitoring oxidation progression. As reported, fuels with high viscosity meeting the international standards have better lubricating quality, which increases the life of the engine [61]. In the same study, there is a relationship between hydrocarbon (HC) emission and viscosity. The HC emissions increase with decreasing viscosity [61]. In our study, the viscosity is lower in all the conditions comparing the standard requirement of EN 14214:2008, but it meets the requirement of ASTM D6751. \begin{table}
\begin{tabular}{l c c c} \hline \hline \multirow{2}{*}{_C:D_} & \multicolumn{3}{c}{**Relative Fatty Acids (\%)**} \\ \cline{2-4}  & **W** & **R** & **RS** \\ \hline \multicolumn{4}{l}{Saturated fatty acids (SFAs)} \\ \hline
14:0 & 8.64 \(\pm\) 0.17 & 7.54 \(\pm\) 0.02 & 8.39 \(\pm\) 0.55 \\
16:0 & 15.18 \(\pm\) 2.64 & 14.80 \(\pm\) 1.80 & 15.24 \(\pm\) 3.67 \\
18:0 & 0.40 \(\pm\) 0.10 & 0.39 \(\pm\) 0.06 & 0.42 \(\pm\) 0.13 \\
20:0 & 0.07 \(\pm\) 0.01 & 0.08 \(\pm\) 0.01 & 0.08 \(\pm\) 0.02 \\
22:0 & 0.16 \(\pm\) 0.01 & 0.19 \(\pm\) 0.01 & 0.20 \(\pm\) 0.02 \\
24:0 & 1.32 \(\pm\) 0.11 & 1.30 \(\pm\) 0.02 & 1.41 \(\pm\) 0.03 \\ \hline \multicolumn{4}{l}{Monounsaturated fatty acids (MUFAs)} \\ \hline
14:1 & 0.08 \(\pm\) 0.02 & 0.09 \(\pm\) 0.01 & 0.08 \(\pm\) 0.01 \\
16:1 & 30.11 \(\pm\) 1.38 & 30.25 \(\pm\) 1.74 & 27.27 \(\pm\) 1.65 \\
18:1 & 1.08 \(\pm\) 0.46 & 1.07 \(\pm\) 0.17 & 1.05 \(\pm\) 0.39 \\
20:1 & 0.04 \(\pm\) 0.02 & 0.06 \(\pm\) 0.02 & 0.08 \(\pm\) 0.03 \\
22:1 & 0.17 \(\pm\) 0.04 & 0.12 \(\pm\) 0.03 & 0.14 \(\pm\) 0.04 \\
24:1 & 0.17 \(\pm\) 0.02 & 0.11 \(\pm\) 0.03 & 0.16 \(\pm\) 0.04 \\ \hline \multicolumn{4}{l}{Polyunsaturated fatty acids (PUFAs)} \\ \hline Omega-3 & & & \\ \hline
18:3n-3 & 0.44 \(\pm\) 0.06 & 0.36 \(\pm\) 0.04 & 0.41 \(\pm\) 0.04 \\
18:4n-3 & 0.21 \(\pm\) 0.06 & 0.21 \(\pm\) 0.03 & 0.23 \(\pm\) 0.05 \\
20:3n-3 & 0.06 \(\pm\) 0.03 & 0.05 \(\pm\) 0.02 & 0.06  
Since this study presents the importance of light as a crucial factor for affecting biomass and lipid content in _P. tricornutum_, it supports its importance in metabolic processes of microalgae in the biotechnology field. However, the specific behavior of each species may be unique with respect to the varied light conditions, as supported by the following evidence studied in an interdisciplinary approach. For example, [PERSON] et al. [62] showed that the fluctuation of red light on blue light spectral distribution affected the metabolic state of cells via increase in non-photochemical quenching and ultimately promoting an increase in carbohydrates, glycolipids, and saturated fatty acids in _Skeletonema marinoi_[62]. In another study, it was observed that different doses of blue wavelengths cause significant alternations in the growth cycle of _Skeletonema marinoi_[63]. The change in the growth pattern and biochemical composition can be referred to the ability of diatoms and microalgae to finely balance the light-harvesting and photoprotective capacity [64; 65; 66; 67].