# Static Magnetic Fields Effects on Polysaccharides Production by Different Microsalgae Strains
## 3 Results
### Characterization of EPS of Cyanobacteria Strains  
The EPS content in the _Spirulina_ and _Arthospira_ biomass obtained for cultures with SMF or controls is showed in Table 2. While the two cyanobacteria are really closed genetically, _Spirulina_ sp. LEB 18 present higher EPS content in the biomass (49.3 g 100 \(\mathrm{g_{biomass}}^{-1}\)) than _Arthospira platensis_ SAG 21.99 (27.9 g 100 \(\mathrm{g_{biomass}}^{-1}\)). However, the first one was cultured outdoor, while the latter was cultured indoor. Moreover, the meta-bibliographic data analysis and experiments conducted by [PERSON], et al. [42] has shown that total carbohydrate content is increased at high temperature with a mean of 41% DW (dry weight) for cultures conducted at more than 36 \({}^{\circ}\)C, and only 27% DW for lower temperatures. Same trend has been observed for high light intensities, with additionally a modulation between glycogen and EPS repartition and a modification in EPS composition. Previous studies with _Spirulina_ under SMF demonstrated an increase in total carbohydrates content [16; 36]. In the present study, application of SMF on _Arthospira platensis_ SAG 21.99 did not significantly increase the EPS content, and this amount even decreased for _Spirulina_ sp. LEB 18 cultures. In addition to the EPS, these cyanobacteria also produce glycogen as storage polysaccharide. Our results thus suggest that the increase in carbohydrate content previously described [16; 36] could be due to a greater accumulation of glycogen within the cells, thus modifying the polysaccharides repartition within cells. This result could also be considered as consistent with what was observed for _Chlorella fusca_, as in both cases the intracellular polysaccharide seems to be enhanced. Analysis of the exopolysaccharidearchides from _A. platensis_ 21.99 and _Spirulina_ sp. LEB 18 have shown that they are mainly constituted of neutral sugars (80-86%) and uronic acids (13-19%) (Table 2). The two different cyanobacteria strains studied had no significant different osidic composition (\(p\leq 0.05\)). However, composition was differently affected, as neutral and acidic sugars were not modified for _Spirulina_ sp. LEB 18, while the uronic acids content increased for _A. platensis_ SAG 21.99. The microalgae photochemical reactions are highly affected by irradiance because there is a biologically unbalanced reaction between the light absorbed by photochemistry versus the energy used by metabolism [58]. [PERSON], et al. [42] have shown that an increase in light intensity could enhance this content. The EPS of cyanobacteria usually includes up to six or more monosaccharides in their structure [11]. Some studies have shown that polysaccharides composition produced by _Spirulina_ is altered by cultivation conditions and extraction methods. These polysaccharides are composed of several monosaccharides, such as rhamnose, ribose, mannose, fucose, galactose, xylose, glucose, glucuronic acid and galacturonic acid [59; 60]. In addition, cyanobacteria have the particularity of producing polymers containing sulphate groups and uronic acids. Additionally, pentoses, such as xylose, arabinose and ribose are monosaccharides frequently found in EPS secreted by cyanobacteria [14]. In our study, the monosaccharide composition was investigated after acidic hydrolysis of the EPS, using HPAEC-PAD. The overall composition of the extracted EPS in cyanobacteria strains is shown in Table 3.