## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**System**} & \multirow{2}{*}{**Strain Number**} & \multirow{2}{*}{**Medium**} & \multirow{2}{*}{**CO\({}_{2}\) (\%)**} & \multicolumn{2}{c}{**Light**} & \multicolumn{2}{c}{**Cultivation**} & \multirow{2}{*}{**Dried Biomass**} & \multirow{2}{*}{**References**} \\  & & & & **Condition** & **Period** & & **Dried Biomass** \\  & & & & **(\mu mol)** & **(Green)** & **Productivity** & **(g\(\cdot\)m\({}^{-2}\cdot\)Day\({}^{-1}\))** & \\  & & & & **Photons** & **(Phae)** & **(g\(\cdot\)m\({}^{-2}\cdot\)Day\({}^{-1}\))** & \\  & & & & **m\({}^{-2}\cdot\)s\({}^{-1}\))** & **(Days)** & & \\ \hline Indoor open & \multirow{2}{*}{26} & \multirow{2}{*}{BG11} & For & 20–350 & \multirow{2}{*}{12} & \multirow{2}{*}{2.2 a} & \multirow{2}{*}{[34]} \\ pond & & & & & pH & & \\ \hline Flask & \multirow{2}{*}{SAG 34/1d} & \multirow{2}{*}{EG:JM} & \multirow{2}{*}{None} & 40 (FL) & \multirow{2}{*}{12} & \multirow{2}{*}{5.52 a} & \multirow{2}{*}{[24]} \\ (250 mL) & & & & & & \\ \hline Flask & \multirow{2}{*}{CCMA-451} & \multirow{2}{*}{BBM} & \multirow{2}{*}{1.5} & 20–30 & \multirow{2}{*}{8} & \multirow{2}{*}{2.88 a} & \multirow{2}{*}{[25]} \\ (3 L) & & & & Continuous & & & \\ \hline Immobilized & \multirow{2}{*}{NIES-144} & \multirow{2}{*}{NIES-N} & \multirow{2}{*}{None} & 150 & \multirow{2}{*}{10} & \multirow{2}{*}{3.7} & \multirow{2}{*}{[2]} \\ biofilm (0.08 m\({}^{2}\)) & & & & Continuous & & & \\ \hline Immobilized & \multirow{2}{*}{SAG 34-1b} & \multirow{2}{*}{BG11} & \multirow{2}{*}{1.5} & 20–100 & \multirow{2}{*}{7} & \multirow{2}{*}{2.3–6.6} & \multirow{2}{*}{[2]} \\ biofilm (0.08 m\({}^{2}\)) & & & & Continuous & & & \\ \hline Immobilized & \multirow{2}{*}{CCAC 0125} & \multirow{2}{*}{Modified \(\text{BG11}\)} & \multirow{2}{*}{1} & 90 (high & \multirow{2}{*}{8} & \multirow{2}{*}{5.4} & \multirow{2}{*}{[28]} \\ biofilm (0.05 m\({}^{2}\)) & & & & & & \\ \hline Angled & \multirow{2}{*}{CCAC 0125} & \multirow{2}{*}{Modified \(\text{BG11}\)} & For & 80 (FL) & \multirow{2}{*}{10} & \multirow{2}{*}{6.49} & \multirow{2}{*}{This study} \\ immobilized & & & & pH & & & \\ biofilm (0.05 m\({}^{2}\)) & & & & pH & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of _H. pluvialis_ green phase cultivation results in an angled biofilm-based photob bioreactor system (this study) with other cultivation systems based on the surface area. However, the addition of CO\({}_{2}\) to the BG11-H medium to ensure a stable environmental pH is necessary. An FL led to a significantly higher growth efficiency than a high-pressure sodium lamp. With the same light intensity, the effective light spectrum from the FL for photosynthesis has been found to reach 60%, which is more efficient than light from the high-pressure sodium lamp at 38% [37]. The growth of _H. pluvialis_ has been demonstrated to be much faster with the use of light from light-emitting diodes (LEDs), the effective spectrum of which can reach over 90%) [38; 39]. However, the FL was still shown to be the optimal light source for the green stage. With the same low light intensity (8 umol photons m\({}^{-2}\cdot\)s\({}^{-1}\)), the use of FLs resulted in more proliferation than red or blue LEDs over a 12-day culture period. The carotenoid ratio was significantly lower [38]. However, the combination of red and blue LEDs showed great promise for simultaneous proliferation with astaxanthin accumulation. Red and blue LEDs are currently being used on pilot-scale TL-PSBRs, resulting in high dry biomass and astaxanthin productivity (unpublished data). Beside dry biomass productivity, the criteria for creating algal biomass in the green phase were the primary purpose of this study. After inoculation on a TL-PSBR, almost all of the cells shed their flagella and rapidly transformed into the green palmella stage [40]. Light from a high-pressure sodium lamp causes algal cells in the biofilm's top layers to change into the red phase even with light intensities below 90 umol photons m\({}^{-2}\cdot\)s\({}^{-1}\).