# Integrated Carbonate-Based CO\({}_{2}\) Capture--Biofixation through Cyanobacteria
## 3 Results
In this condition, the plastoquinone reduction rate exceeds the electron delivery rate, and an excess number of photons remains unused as all the charge carriers are busy [35]. Due to these results, in all the following experiments, the light PPFD was set at the lowest explored value of 260 \(\upmu\)mol/s\(\cdot\)m\({}^{2}\), with a benefit on the energy requirements and replication of the lab-scale performances during (future) scale-up. The influences of individual parameters on P for \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**n.**} & **T** & **Light Intensity** & **NaHCO\({}_{3}\)** & **P Spr01** & **R Spr01** & **P Spr02** & **R Spr02** \\  & **(\({}^{\circ}\)C)** & **(\(\upmu\)mol/s\(\cdot\)m\({}^{2}\))** & **(mol/L)** & **(mg/L\(\cdot\)d)** & **(mgCO\({}_{2}\)/L\(\cdot\)d)** & **(mg/L\(\cdot\)d)** & **(mgCO\({}_{2}\)/L\(\cdot\)d)** \\ \hline
1 & 29 & 260 & 0.36 & \(180\pm 16\) & \(300\pm 28\) & \(500\pm 17\) & \(870\pm 30\) \\
2 & 29 & 390 & 0.09 & \(220\pm 20\) & \(360\pm 35\) & \(350\pm 12\) & \(610\pm 21\) \\
3 & 35 & 260 & 0.36 & \(240\pm 21\) & \(390\pm 37\) & \(720\pm 25\) & \(1250\pm 43\) \\
4 & 32 & 260 & 0.23 & \(220\pm 20\) & \(360\pm 35\) & \(580\pm 20\) & \(1010\pm 35\) \\
5 & 35 & 390 & 0.36 & \(200\pm 17\) & \(310\pm 30\) & \(760\pm 26\) & \(1320\pm 45\) \\
6 & 29 & 390 & 0.36 & \(140\pm 13\) & \(230\pm 22\) & \(600\pm 21\) & \(1050\pm 36\) \\
7 & 35 & 390 & 0.09 & \(190\pm 17\) & \(300\pm 29\) & \(290\pm 10\) & \(500\pm 17\) \\
8 & 32 & 260 & 0.23 & \(150\pm 13\) & \(240\pm 23\) & \(530\pm 18\) & \(920\pm 32\) \\
9 & 35 & 260 & 0.09 & \(190\pm 17\) & \(310\pm 30\) & \(290\pm 10\) & \(500\pm 17\) \\
10 & 32 & 260 & 0.23 & \(150\pm 13\) & \(240\pm 23\) & \(470\pm 16\) & \(820\pm 28\) \\
11 & 29 & 260 & 0.09 & \(210\pm 19\) & \(340\pm 32\) & \(290\pm 10\) & \(500\pm 17\) \\ \hline \hline \end{tabular}  
* Common conditions: 72 h, 0.09M NaHCO\({}_{3}\) inoculum. Mean values of two replicates.  
\end{table} 
Table 1: DoE conducted experiments and output data *  
Figure 3: Daily growth rates for Spr01 (**a**) or Spr02 (**b**). the Spr02 strain are shown in Figure 4, from which it can be observed that there is a strong dependency on bicarbonate concentration and a slight dependence on temperature. The influence of simultaneous variation of significant parameters on P is shown in Figure 5 (see also Figure S4). A strong interaction between the two parameters can be detected (AC, Figure S3b). In fact, at low bicarbonate conc. values (0.09 M), the dependence of P on T is small, while at higher values (0.36 M), P depends strongly on temperature. In other words, a positive synergistic effect occurs between temperature and bicarbonate concentration. Figure 4: Influence of NaHCO\({}_{3}\) conc. (**a**) and temperature (**b**) on P for Spr02 strain. Figure 5: Contour plot (**a**) and surface plot (**b**) of the dependence of P from NaHCO\({}_{3}\) concentration and T for Spr02 strain. The best productivity values were obtained at the highest values of both NaHCO\({}_{3}\) (0.36 M) and T (35 \({}^{\circ}\)C). This could mean that an increased P value could correspond to ranges external to the investigated domain, an eventuality also suggested by growth rates reported in Figure 3b. Anyway, as the final pH value of 12.2 suggests, the maximum seemed very near. While exploring temperatures greater than 35 \({}^{\circ}\)C was judged of little interest due to the energy requirement in the case of further scale-up of the integrated CCS-biofixation system, using higher bicarbonate concentrations is desirable, as it is linked to the reduction in operating volumes required to transport the same amount of CO\({}_{2}\).