## 3 Results and Discussion
### Biochemical Composition
#### 3.4.2 Fatty Acid Profile  
In order to assess the lipid composition of the biomass, the fatty acid profile was analyzed (Table 3). The FAME profile of C. _amblystomatis_ is dominated by C16:4\(n\)-3 (21.94%-23.65% of total fatty acids; TFA), C16:0 (15.24%-19.29% of TFA), C18:4\(n\)-3 (8.61%-8.83% of TFA), C18:3\(n\)-3 (27.58%-31.40% of TFA) and C18:1 (5.34%-6.27% of TFA). Interestingly, this microalga contains a high content of polyunsaturated fatty acids (PUFAs), reaching 74.70% of TFA in the biomass produced in the 2.5-m\({}^{3}\) PBR, which is significantly higher than the 67.10% of TFA detected in the biomass obtained from the 10-m\({}^{3}\) PBR (\(p<0.05\)). Saturated fatty acids (SFAs) and monoussaturated fatty acids (MUFAs) are similar between the reactors.  
Overall, the FAME profile does not match with previous values reported for other _Chlorococc_ microalgae, wherein the FAME profile combines higher percentages of SFAs and MUFAs, and lower contents of PUFAs [39; 40], reinforcing the conclusion that _C. amblystomatis_ is a species distinct from those whose fatty acid profiles have been described previously.  
PUFAs are classified as \(n\)-3 and \(n\)-6 and play an important role in human and animal nutrition [41; 42]. It is reported that \(n\)-3 fatty acids play an important role in the prevention of coronary heart disease and inflammatory disease, brain disorder, such as Alzheimer's disease and help in cancer therapy [43; 44; 45], while \(n\)-6 fatty acids are pro-inflammatory [41; 46]. The functional sources of \(n\)-3 in microalgae are normally eicosapentaenoic (EPA, C20:5\(n\)-3) and docosahexaenoicenoic (DHA, C22:6\(n\)-3) acids; however, chlorophytes and particularly freshwater microalgae are, in general, deficient in both C20 and C22 PUFAs [4; 45]. Nevertheless, there are other important PUFAs such as linoleic (LA, C18:2\(n\)-6), \(\alpha\)-linolenic (ALA, C18:3\(n\)-3) and \(\gamma\)-linolenic (GLA, C18:3\(n\)-6) acids with proven biomedical and nutraceutical applications [42]. Furthermore, once consumed, these fatty acids are metabolized within mammalian cells. Thereby, ALA is converted to stearidonic (C18:4\(n\)-3) and eicosatetraenoic (C20:4\(n\)-3) acids to form EPA, which is further metabolized to DHA (C22:6\(n\)-3) [41; 47]. Although the \(n\)-3 and \(n\)-6 PUFAs biosynthetic pathways share the same series of enzymes, the health effects are dependent on the \(\Sigma n\)-6/\(\Sigma n\)-3 ratio [41; 46; 47], which is recommended to be lower than 10 by the World Health Organization (WHO) in order to prevent inflammatory, cardiovascular and nervous system disorders [46; 47]. Therefore, since _C. amblystomatis_, presents a PUFA/SFA ratio of 4.30-2.81 and a \(\Sigma n\)-6/\(\Sigma n\)-3 ratio of 0.10-0.13, this strain can be considered as a good alternative source of dietary PUFA.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Reactor** & **Proteins (\%)** & **Lipids (\%)** & **Carbohydrates (\%)** & **Ashes (\%)** \\ \hline
2.5-m\({}^{3}\) PBR & 55.72 \(\pm\) 2.85 a  & 18.33 \(\pm\) 0.97 b  & 17.43 \(\pm\) 3.58 a  & 9.88 \(\pm\) 5.87 a  \\
10-m\({}^{3}\) PBR & 48.22 \(\pm\) 0.43 b  & 31.44 \(\pm\) 4.10 a  & 5.78 \(\pm\) 3.99 b  & 15.85 \(\pm\) 5.00 a  \\ \hline \end{tabular}
\end{table}
Table 2: Biochemical composition of _Chlorococc_ _amblystomatis_ biomass grown in the 2.5- and 10-m\({}^{3}\) tubular photobioreactors (PBR). Proteins, lipids, and carbohydrates are presented as the percentage of biomass dry weight (DW). Different letters indicate significant differences between reactors. Values are given as means \(\pm\) standard deviation (\(n=3\)).