## 3 Results and Discussion
### Biochemical Composition
#### 3.4.1 Proximate Composition  
The content of proteins, lipids, carbohydrates, and ashes detected in the biomass produced in both PBRs is presented in Table 2.  
The results obtained revealed that proteins are the main macronutrient present in _C. amblystomatis_ biomass. The highest protein content was achieved in microalgal cells grown in the 2.5-m\({}^{3}\) PBR, reaching more than 55% of their DW (\(p<0.05\)), while the biomass produced in the 10-m\({}^{3}\) PBR registered a protein content of 48% DW. Microalgal proteins are appreciated as an additive to feed for a wide variety of animals ranging from fish (aquaculture) to pets and farm animals and are very interesting for functional food applications due to their demonstrated biological activities impacting different  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Reactor**} & \multicolumn{2}{c}{**Volumetric Productivity**} & \multicolumn{2}{c}{**Areal Productivity**} & \multirow{2}{*}{\(\mu\)} & **PE** \\  & \multicolumn{2}{c}{**(g\(\cdot\)L\({}^{-1}\)-d\({}^{-1}\))**} & & **(g\(\cdot\)m\({}^{-2}\)-d\({}^{-1}\))** & **(d\({}^{-1}\))** & **(\%)** \\  & **Maximum** & **Global** & **Maximum** & **Global** & \\ \hline
0.25-m\({}^{3}\) FP & 0.27 \(\pm\) 0.02 a & 0.07 \(\pm\) 0.00 a & 23.21 \(\pm\) 1.50 a & 5.94 \(\pm\) 0.41 a & 0.16 \(\pm\) 0.00 a & 0.73 \(\pm\) 0.02 a \\
2.5-m\({}^{3}\) PBR & 0.26 \(\pm\) 0.02 a & 0.09 \(\pm\) 0.02 a & 26.75 \(\pm\) 2.47 a & 8.65 \(\pm\) 1.62 a & 0.13 \(\pm\) 0.03 a & 1.33 \(\pm\) 0.12 b \\
10-m\({}^{3}\) PBR & 0.09 \(\pm\) 0.03 b & 0.05 \(\pm\) 0.01 b & 36.56 \(\pm\) 1.52 b & 14.84 \(\pm\) 3.98 b & 0.16 \(\pm\) 0.02 a & 1.84 \(\pm\) 0.18 c \\ \hline \hline \end{tabular}
\end{table}
Table 1: Maximum volumetric productivity, overall volumetric productivity, maximum areal productivity and overall areal productivity, specific growth rate (\(\mu\)) and photosynthetic efficiency (PE) of pilot- and industrial-scale tubular photobioreactors (PBR). Different letters indicate significant differences between reactors. Values are given as means \(\pm\) standard deviation (\(n=3\)).  
human health conditions [3; 9]. The lower value of protein ratio obtained in the biomass grown in the 10-m\({}^{3}\) PBR was probably due to exposure of the cultures to stressful conditions. Even though the accumulation of carbohydrates in microalgae is mainly due to the net balance between photosynthesis and respiration [36], it would be expected that the biomass grown in the 10-m\({}^{3}\) PBR showed the highest value of carbohydrates, since it was exposed to higher light irradiance. However, it was in the biomass grown in the pilot-scale PBR that the highest percentage of carbohydrates was detected, achieving 17.43% of biomass DW (\(p<0.05\)), within the range of reported values for the majority of microalgae [4; 9]. Indeed, under unfavorable conditions (e.g., high irradiance and nitrogen limitation), the excess of carbon fixed during photosynthesis may have been diverted into storage compounds such as lipids or carbohydrates [4; 9; 37; 38]. This could also explain the higher lipid content observed in the biomass grown in the 10-m\({}^{3}\) PBR (\(p<0.05\)), 31.44% DW, in comparison to that of microalgal cells grown in the 2.5-m\({}^{3}\) PBR (18.33%).