# Exopolysaccharides from Cyanobacteria: Strategies for Bioprocess Development
## 3 Cyanobacterial Bioprocess (Cyano-EPS) Development
### Production and Optimization
#### 3.2.4 Design of Experiments  
Optimization refers to the discovery of the conditions of a system, a process, or a product to obtain the maximum benefit from it [97]. The classical methods involve the optimization of just one condition at a time, a methodology highly applied in Cyano-EPS (see Table 3). The optimization method must take into account all the interactions and the optimum conditions obtained are validated. The design of experiments is highly used in bioprocess optimization, though the examples in Cyano-EPS are less frequent. A central composite design (CCD) was applied to _Cyanothece epiplytia_ to evaluate the combined effect of micronutrients magnesium and iron [62]. A full factorial design was applied _Arthospira_ sp. for the combination of NaCl and light intensity factors [89]. The same experimental design was applied to _A. platensis_ strain \"Compere 1968/3786\" under photoautotrophic [98] and mixotrophic modes [68]. Temperature highly affected growth and EPS production when compared to light intensity; however, the combination of temperature and light were also found to be significant, while growth and EPS production had different optima settings [98]. Light intensity and glucose concentration were investigated under mixotrophic conditions. In this case, EPS titer and yield were mostly affected by glucose concentration with divergent optimal set points [68].  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Strains**} & \multicolumn{2}{c}{**Optimization Factor**} & \multicolumn{1}{c}{**EPS Tite/Productivity**} & \multirow{2}{*}{**Literature**} \\ \cline{2-2} \cline{4-5}  & **Culture Media** & **Process Parameters** & \multicolumn{1}{c}{**/Yield**} & \multicolumn{1}{c}{**Literature**} \\ \hline \multicolumn{5}{c}{**Nostocales**} \\ \hline _Anahenna apstrantis_ & & nd\(\dagger\) & Fed-batch; Film forming PBR & 14.73 mg/g (CPS) & [51] \\ VRUC163 & & & & \\ \hline _Anahenna cylindrica_ & N source (**NaNOg**) & nd\(\dagger\) & 2.36 mg/L (RPS) & [58] \\
10 C & Mixotrophy & & & \\ \hline _Anahenna WSAF_ & N source (**abscene**; **NaNOg**); & L/D cycle (**continuous**); Shear & & \\  & P source (**\(\mathbf{k_{2}}\)PHQ**); & stress (**zeration**); & & \\ \hline _Anahenna sp. ATCC_ & N source (\(\mathbf{N_{2}}\), KNO3; NH4 Cl); Salinity & Temperature; Light intensity (**medium**); Shear stress (**high** aeration); **Dilution rate** & \(1100\) mg/L/day (RPS + CFS) & [70] \\ \hline _Anahenna sp._ & & & & \\ \hline _Anahenna twolosa_ & nd\(\dagger\) & Initial pH (**8.5**) & 1.7 g/L (RPS) & [48] \\ \hline _Anahenna twolosa_ & N source (**abscene**; **NaNOg**); & L/D cycle (**continuous**); Shear stress (**zeration**); & & \\ \hline _Cyanospina capsulata_ & & & & \\ \hline \multirow{2}{*}{_Nostoc flagelliforme_} & N source (**NaNOg**); P source (**K2 PHQ**); & Temperature (low); **Light intensity (**high); Initial pH (**4 kaline**) & 14.29 mg/L/day (RPS) & [57] \\ \hline _Nostoc flagelliforme_ & ndt & Cultivation mode (**Fed-batch**); pH (8–9) & 8.86 mg/L/day (CPS) & [72] \\ \hline _Nostoc flagelliforme_ & nd\(\dagger\) & light quality (monochromatic **red**, yellow, green, **blue**, **blue**) & 47.39 mg/g (RPS) & [79] \\ \hline _Nostoc flagelliforme_ & nd\(\dagger\) & light quality (white fluorescent and monochromatic **red**, yellow, green, blue, **purple**); Red light intensity (**medium**) & 275 mg/g (CPS) & [80] \\ \hline _Nostoc flagelliforme_ & C source (abscene; **NaHCO3**); N source (**abscene**; **NaNOg**) & light quality (monochromatic red, **blue**) & nd\(\dagger\) & [63] \\ \hline \multirow{2}{*}{_Nostoc flagelliforme_} & N source (**Urea**, NaNOg**, NH4 Cl; **Arginine**) & Light intensity (**low**); Light quality (mixed wavelengths, **red, blue, green); **Wavelength shift** & 5.42 mg/L/day (RPS) & [61] \\ \hline _Nostoc flagelliforme_ & C source (glucose); Salinity (**NaCI**) & nd\(\dagger\) & 234.82 mg/g (CPS) & [84] \\ \hline _Nostoc sp._ & nd\(\dagger\) & Light intensity (**high**) & 134.26 mg/g DW (RPS) & [85] \\ \hline _Nostoc sp._ & & & & \\ \hline _Nostoc sp.