## 3 Results and Discussion
### Production of Metabolites under Various Growth Conditions
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Strain** & **Cultivation** & **Culture** & **Photoperiod** & **Biomass Yield** & **Biomass Yield** & **Specific** & \\
**System** & **Cultiven** & **Medium** & **Photons m\({}^{-2}\)** & **(g L\({}^{-1}\))** & **Productivity** & **Growth Rate** & **Reference** \\  & & & & **s\({}^{-1}\)/CO\({}_{2}\) (\%)** & & **(g L\({}^{-1}\) Day\({}^{-1}\))** & **(Day\({}^{-1}\))** & **Reference** \\ \hline _Scenedesmacae_ & Labfors & & & & & & \\ strain EZ-B1 & photobioreactor & Modified BBM & 24/1300/2 & 5.23 & 0.69 & 0.72 & This study \\ _Desmodesmins_ & Glass bottle & BG-11 & 16/300/4 & 3.53 & 0.54 & ND & [45] \\ _Scenedesmus_ sp. & Glass bottle & BG11 & 24/80/20 & 1.95 & 0.12 & 0.57 & [52] \\ _Scenedesmus_ & Flasks & Modified BBM & 24/60/0.03 & 0.52 & 0.02 & 0.04 & [53] \\ _obtensus_ & Photobioreactor & BG-11 & 24/100/10 & 3.92 & 0.49 & ND & [54] \\ _Desmodesmins_ & & & & & & & \\ _subspictus_ & Photobioreactor & Modified BG11 & 24/100/5 & 1.4 & 0.20 & 0.41 & [55] \\ _Desmodesmins_ & Flasks & TAP & 24/200/0.03 & 1.54 & 0.11 & 0.27 & [56] \\ _Scenedesmus_ sp. & Flasks & BG11 & 16/110/5 & 1.10 & 0.08 & ND & [57] \\ _Tetradesmus_ & Photobioreactor & Determer’s & & & & & \\ _obliquus_ ESP-5 & & Medium & 24/150/2.5 & 3.38 & 0.45 & ND & [58] \\ \hline \hline \end{tabular} ND—not determined.  
\end{table} 
Table 3: Comparison of biomass yield, biomass productivity, and specific growth rates of various _Scenedesmacae_ strains under different optimal growth conditions (batch treatments). Proteins obtained from microalgae are a promising alternative to animal and plant proteins [66]. The protein content varies sharply among different species of microalgae, ranges from 12 to 70% of dry weight, and also depends on the cultivation conditions [67]. In this study, the protein content in cells of _Scenedesmacae_ strain EZ-B1 increased with increasing light intensity with a 16 h photoperiod, but under continuous light conditions (112.32 mol m\({}^{-2}\) day\({}^{-1}\)), the protein content was lower (Figure 5). The maximum protein content in the biomass of the strain was 30.5 \(\pm\) 3.4% of dry weight with a 16 h photoperiod and 112.32 mol m\({}^{-2}\) day\({}^{-1}\). Additionally, it was found that, regardless of the carbon dioxide concentration, at the same high light intensity, the protein content was at the same level (17-18% of dry weight). It is worth considering that the protein content in the dry biomass of algal cells was determined at the end of cultivation; therefore, differences may be associated not only with the tested growth conditions but also with the time when the culture entered the stationary phase of growth (a change in the cultivation period can cause a change in the ratio of cellular metabolites). Figure 4: Concentrations of total carotenoids of _Scenedesmacae_ alga, strain EZ-B1, at 64, 136, and 208 h of cultivation under periodic light (PL; **A**) and continuous light (CL; **B**). Changing light intensity in the range of 130-520 umol m\({}^{-2}\) s\({}^{-1}\) did not affect the protein content in cells of _C. vulgaris_ when grown in closed bioreactor, as was shown in a study performed by [PERSON] et al. [68]. However, in another study, when _C. vulgaris_ was cultivated at the maximum light intensity tested (300 \(\mu\)E m\({}^{-2}\) s\({}^{-1}\)), the protein content was 1.46\(\times\) higher compared to the minimum intensity [69]. When studying the effect of photoperiod on the synthesis of various metabolites in _S. acutus_[31], it was revealed that under 24 h and 18 h photoperiods, the maximum protein content was reached on day 10, while with a 12 h photoperiod, the maximum concentration was achieved on day 8. However, the maximum protein content did not differ significantly between different photoperiods. This is probably due to the light intensity, which was only 55 umol photons m\({}^{-2}\) s\({}^{-1}\). In the work presented here, the final biomass protein content decreased under a 24 h photoperiod at the maximum average daily PPFD.