# Static Magnetic Fields Effects on Polysaccharides Production by Different Microsalgae Strains
## 3 Results
### Characterization of EPS of Cyanobacteria Strains
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Assays** &
\begin{tabular}{c} **EPS (\(\mathbf{g}\)**\(\mathbf{\cdot}\)**100** \\ \(\mathbf{S}_{\mathbf{biomass}}\)**\(\mathbf{}^{\mathbf{-1}}\))** \\ \end{tabular} & **\% NS in EPS** & **\% UA in EPS** & \(\mathbf{X}_{\mathbf{max}}\) **(g L L\({}^{\mathbf{-1}}\))** \\ \hline \multicolumn{5}{c}{_Arthospira platensis_ SAG 21.99} \\ \hline Control & 27.9 \(\pm\) 0.01  & 86.83 \(\pm\) 0.01  & 13.17 \(\pm\) 0.01  & 0.59 \(\pm\) 0.04  \\ SMF 24 h d\({}^{-1}\) & 34.8 \(\pm\) 0.90  & 80.72 \(\pm\) 2.34  & 19.27 \(\pm\) 2.34  & 0.78 \(\pm\) 0.05  \\ SMF 1 h d\({}^{-1}\) & 19.4 \(\pm\) 0.06  & 81.51 \(\pm\) 0.01  & 18.49 \(\pm\) 0.01  & 0.88 \(\pm\) 0.04  \\ \hline \multicolumn{5}{c}{_Spirulina_ sp. LEB 18} \\ \hline Control & 49.3 \(\pm\) 0.19  & 84.47 \(\pm\) 2.27  & 15.53 \(\pm\) 0.01  & 3.40 \(\pm\) 0.01  \\ SMF 24 h d\({}^{-1}\) & 33.8 \(\pm\) 0.49  & 85.01 \(\pm\) 3.10  & 15.00 \(\pm\) 3.10  & 3.37 \(\pm\) 0.01  \\ SMF 1 h d\({}^{-1}\) & 33.1 \(\pm\) 0.06  & 82.98 \(\pm\) 0.35  & 17.02 \(\pm\) 0.35  & 3.65 \(\pm\) 0.06  \\ \hline \hline \end{tabular}  
Means \(\pm\) standard deviations. Different letters in the same column correspond to significant differences for the same microalgae strain (\(p\leq 0.05\)). EPS: exopolysaccharidearchides, NS: Neutral Sugars, UA: Uronic Acids.  
\end{table} 
Table 2: Exopolysaccharidearchides (EPS) production yield and global osidic composition. The strains studied exhibited eight different monosaccharides in their compositions (fluose, arabin, mannose, galactose, glucose, xylose, glucuronic acid and galacturonic acid). These compositions are thus in accordance with those previously published. The main monosaccharide found in _A. platensis_ 21.99 EPS was glucose, that represents around 70% of the overall composition for the control, while in _Spirulina_ sp. LEB 18 biomass, galactose and glucose are the highest constituents. [PERSON], et al. (2019) showed that the cyanobacteria cultured with irradiance up to 800 \(\mu_{\text{mophotons}}\) m\({}^{-2}\) s\({}^{-1}\) presented strong increase in glucose content, reaching 77.7%, showing that a modulation of EPS composition can be encountered with cultivation conditions. The difference in EPS composition for the controls of the two cyanobacteria could thus be due to the different culture conditions (indoor and outdoor). However, regarding _A. platensis_ SAG 21.99, the SMF applied for 24 h and 1 h showed some monosaccharides that are not found in the control assay, or their amount is higher than control, such as fucose, rhamn, galactose and glucuronic acid. At the opposite, the SMF application decreased the glucose, arabin and xylose concentrations. For _Spirulina_ sp. LEB 18 cultured with SMF, differences appeared less significant, but slight increases were observed for fucose, galactose, glucose and glucuronic acid (Table 3). These cyanobacterial EPS compositions are then in accordance with literature data, especially regarding glucose and galactose content. Glucose is the main monosaccharide in compositions and galactose, the secondary in cyanobacteria and other microalgae strains ([PERSON] et al., 2019; [PERSON] et al., 2019). Xylose is often encountered in EPS compositions, since xylans could be a protective mechanism for cells to resist mechanical stress. Biomass cultured under SMF applied for 1 h produced more xylose, as it may be a protection against SMF stress. As EPS from microalgae and cyanobacteria are known to exhibit biological activities, the modulation of some monosaccharide that was observed in this study could have significant importance for the potential applications associated to these EPS. Furthermore, in the end of microalgal cultivation when the nutrient content is low and there is high algal density, EPS could be used as carbon and energy source ([PERSON] et al., 2019; [PERSON] et al., 2019).