## 3 Results and Discussion
### Biochemical Composition
#### 3.6.3 Chlorophylls and Carotenoids Contents  
The content of carotenoids and chlorophylls of _C. amblystomatis_ was evaluated (Table 10).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**FAME**} & \multicolumn{2}{c}{**Hetetrotrophy**} & \multicolumn{2}{c}{**Photoautotrophy**} \\ \cline{2-4}  **\%** & **Basal** & **Optimized** & **Basal** & **Optimized** \\ \hline C14:0 & 0.88 \(\pm\) 0.05 \({}^{\text{a}}\) & 0.66 \(\pm\) 0.03 \({}^{\text{b}}\) & 0.66 \(\pm\) 0.00 \({}^{\text{b}}\) & nd \\ C16:4\(n\)-3 & 14.09 \(\pm\) 0.14 \({}^{\text{b}}\) & 1  
Pigments are high-value products that are synthesized naturally under photoautotrophic conditions. Nevertheless, some pigments can be produced in heterotrophic dark conditions but at lower concentrations [11; 38]. Thereby, as expected, the _C. amblystomatis_ cultures grown in heterotrophic conditions registered a decreased content of pigments globally compared to cultures grown in photoautotrophic conditions (\(p<0.05\)), except for \(\beta\)-carotene.  
_C. amblystomatis_ registered lower chlorophyll content values than those previously reported (40.24 mg\(\cdot\)g\({}^{-1}\) in 2.5 m\({}^{3}\) tubular photobioreactor) [35]. Under heterotrophic growth, this microalga registered 8.53-14.59 mg\(\cdot\)g\({}^{-1}\) of chlorophyll \(a\) and \(b\), and under photoautotrophy, they registered 12.88-29.32 mg\(\cdot\)g\({}^{-1}\). Chlorophylls are mainly used as a natural food dye and have several reported human health benefits due to their antioxidant and anti-inflammatory properties [38; 39]. Besides chlorophylls, carotenoids are the second most abundant pigment group [11]. The main carotenoids in the _C. amblystomatis_ profile were lutein and \(\beta\)-carotene, with 1.23-1.60 mg\(\cdot\)g\({}^{-1}\) and 4.32-5.27 mg\(\cdot\)g\({}^{-1}\) of lutein, and 0.81-4.15 mg\(\cdot\)g\({}^{-1}\) and 5.37-5.84 mg\(\cdot\)g\({}^{-1}\) of \(\beta\)-carotene in heterotrophy and photoautotrophy, respectively. Carotenoids are strong antioxidants and have been described to prevent several cardiovascular and neurodegenerative diseases, cancer, diabetes, and macular degeneration [40]. \(\beta\)-carotene plays an important role in human nutrition because it acts as provitamin A, being converted into vitamin A in vivo [41; 42]. Vitamin A deficiency represents a global problem in developing countries, and it is related to human visual malfunction and decreased immune function [41; 43]. Lutein is among the most important carotenoids in the human diet (as a food colorant) and prevents macular degeneration [43; 44]. _C. amblystomatis_ registered high lutein content, similar to the main lutein producers _Muriellopsis_ sp. (4.3 mg\(\cdot\)g\({}^{-1}\)) and _Scenedesmus almeriensis_ (4.5 mg\(\cdot\)g\({}^{-1}\)) [45]. The main application of microalgae as lutein producers is as feed additive in aquaculture [44; 45] and poultry livestock.  
_C. amblystomatis_ also registered a high content of neoxanthin in the cultures grown with optimized photoautotrophic medium (3.66 mg\(\cdot\)g\({}^{-1}\)). Neoxanthin was reported to significantly reduce the risk of prostate cancer, proving to be one of the strongest carotenoids with antiproliferative effects on human prostate cancer cells [46].  
Finally, it is worth mentioning that the global carotenoids market size had already reached USD 1.44 billion in 2019 and is expected to rise to USD 1.84 billion by 2027 [47]. Indeed, higher demand for natural sources of pigments has been observed over the last years, and, therefore, _C. amblystomatis_ presents great pigment content even without any biosynthesis induction, which is promising in the context of these market opportunities.