## 3 Results and Discussion
### Biochemical Composition
#### 3.6.2 Fatty Acids Profile  
In order to evaluate the lipid composition, the fatty acid methyl esters (FAME) profile was analyzed (Table 9). FAME contents below 0.50% of total fatty acids were excluded.  
\begin{table}
\begin{tabular}{c c c c c c} \hline  & **Medium** & **Proteins (\%)** & **Lipids (\%)** & **Carbohydrates (\%)** & **Ashes (\%)** \\ \hline \multirow{2}{*}{Hetero.} & Basal & 33.49 \(\pm\) 0.38 \({}^{\mathrm{d}}\) & 7.41 \(\pm\) 1.89 \({}^{\mathrm{c}}\) & 47.68 \(\pm\) 2.19 \({}^{\mathrm{a}}\) & 11.42 \(\pm\) 0.07 \({}^{\mathrm{c}}\) \\ \cline{2-6}  & Optimized & 61.49 \(\pm\) 0.13 \({}^{\mathrm{b}}\) & 8.88 \(\pm\) 0.70 \({}^{\mathrm{c}}\) & 14.11 \(\pm\) 0.58 \({}^{\mathrm{b}}\) & 15.52 \(\pm\) 0.24 \({}^{\mathrm{b}}\) \\ \hline \multirow{2}{*}{Photoauto.} & Basal & 56.67 \(\pm\) 1.06 \({}^{\mathrm{c}}\) & 19.74 \(\pm\) 1.07 \({}^{\mathrm{a}}\) & 4.26 \(\pm\) 0.47 \({}^{\mathrm{c}}\) & 19.39 \(\pm\) 1.53 \({}^{\mathrm{a}}\) \\ \cline{2-6}  & Optimized & 73.45 \(\pm\) 1.91 \({}^{\mathrm{a}}\) & 13.28 \(\pm\) 0.45 \({}^{\mathrm{b}}\) & 8.23 \(\pm\) 0.02 \({}^{\mathrm{c}}\) & 6.07 \(\pm\) 0.07 \({}^{\mathrm{d}}\) \\ \hline \end{tabular}
\end{table}
Table 8: Proximate composition of biomass with hetero- and photoautotrophic basal and optimized media. Proteins, lipids, carbohydrates, and ashes are presented as the percentage of the biomass dry weight. Different letters indicate significant differences between media. Values are given as means \(\pm\) standard deviation (\(n=3\)).  
The dominant FAME in the heterotrophic cultures of _C. amblystomatis_ was C16:0 (30.95-32.33% of total fatty acids; TFA), while in the photoautotrophic cultures, it was C18:3\(n\)-3 (28.46-34.26% of TFA), which was not detected in the heterotrophic cultures. The second most abundant FAME was C16:4\(n\)-3 (14.09-18.635% of TFA), followed by C18:2\(n\)-6 (5.38-13.38% of TFA), C18:3\(n\)-6 (4.47-10.30% of TFA), C18:1 (1.54-11.46% of TFA), and C16:1 (1.21-9.68% of TFA). The remaining FAME values were similar between the cultures grown in both the hetero- and photoautotrophic conditions.  
Furthermore, the prevalent polyunsaturated fatty acids (PUFAs) were more abundant in the photoautotrophic cultures (70.46-72.82% of TFA) compared to the heterotropically grown cultures (44.47-51.64% of TFA). On the contrary, monosaturated fatty acids (MUFA) displayed higher concentrations in heterotrophic biomass (13.08-21.14% of TFA) compared to the photoautotrophic cultures (3.27-3.31% of TFA; \(p<\) 0.05). Lastly, the amount of saturated fatty acids (SFA) was slightly higher in heterotrophic cultures (34.39-35.28% of TFA) in comparison to the photoautotrophic ones (23.87-26.27% of TFA).  
The \(\Sigma n\)-6/\(\Sigma n\)-3 ratio plays an important role in human health, being recommended by the World Health Organization to be lower than 10 to prevent a negative impact on human health since \(n\)-6 PUFAs are pro-inflammatory whereas \(n\)-3 PUFAs are anti-inflammatory [36, 37]. All hetero- and photoautotrophic cultures registered a \(\Sigma n\)-6/\(\Sigma n\)-3 ratio from 0.2 to 1.37 and more PUFA content in comparison to SFAs (with PUFA/SFA ratio above 1, from 1.29 to 3.06). Thereby, _C. amblystomatis_ might represent an interesting source of PUFAs.