# Cyanobacterial Potential for Restoration of Loess Surfaces through Artificially Induced Biocrusts
## 3 Results
### Screening of Cyanobacterial Strains for Toxin, Biomass and Polysaccharide Production
#### 3.1.3 Polysaccharide Production  
The production of RPSs and total polysaccharides by isolated strains is summarized in Table 3. The production of RPSs and total polysaccharides was proportional in both growth media. The highest observed amounts per liter of RPSs and total polysaccharides were produced by _Tolytotrix_ sp. L4 strain cultivated in the BG11 N+ medium (2.7 \(\pm\) 0.1 mg/L and 7.1 \(\pm\) 0.6 mg/L, respectively). The highest amounts of RPSs and total polysaccharides among strains cultivated in the BG11 N\(-\) medium was observed in the _Nostoc_ L6 strain (1.6 \(\pm\) 0.1 mg/L and 3.7 \(\pm\) 0.2 mg/L, respectively). The presence of nitrate in the cultivation media had an effect on polysaccharide production. The potential of isolated strains to release polysaccharides into their surrounding was estimated by the share of RPSs in the total amount of polysaccharides (Table 3, RPS share). Four of five strains (_Chroococcidiposis_ sp. L1, _Nostoc_ sp. L2, _Tolytotrix_ sp. L4, _Nostoc_ sp. L5) showed the ability to excrete a higher portion of polysaccharides when grown in the BG11 N+ medium. The potential of these strains for polysaccharide production was assessed by calculating the specific polysaccharide production in each strain. The production of RPSs and total polysaccharides were correlated with their biomass (Table 3, total polysaccharide and RPS yield). Strain _Chroococcidiposis_ sp. L1 showed the highest total polysaccharide and RPS yield when cultivated in diazotrophic conditions by producing 196.6 mg/g biomass and 77.4 mg/g biomass, respectively. However, such yields are 'falsely' high since at the time of polysaccharide analyses (7 th week of cultivation) a drastic decrease of biomass production by the strain _Chroococcidiposis_ sp. L1 was observed. If the observations of the yields of strain L1 in the medium BG11 N\(-\) are excluded, the two highest RPS and total \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Strain** & **Med.** & **1 st Week** & **2 nd Week** & **3 rd Week** & **4 th Week** & **5 th Week** & **6 th Week** & **7 th Week** \\ \hline \multirow{2}{*}{L1} & N+ & 6.2 \(\pm\) 1.0 & 18.1 \(\pm\) 1.0 & 23.7 \(\pm\) 1.7 & 31.6 \(\pm\) 1.0 & 39.5 \(\pm\) 1.9 & 50.8 \(\pm\) 4.5 & **63.8 \(\pm\) 2.6** \\  & N\(-\) & 5.7 \(\pm\) 1.0 & 18.6 \(\pm\) 1.7 & 23.7 \(\pm\) 1.7 & **34.4 \(\pm\) 2.6** & 19.2 \(\pm\) 1.0 & 14.1 \(\pm\) 1.0 & 7.9 \(\pm\) 1.0 \\ \hline \multirow{2}{*}{L2} & N+ & 16.4 \(\pm\) 1.0 & 50.3 \(\pm\) 2.6 & 55.9 \(\pm\) 2.9 & 69.4 \(\pm\) 4.5 & 89.8 \(\pm\) 11.9 & 112.9 \(\pm\) 1.9 & **139.5 \(\pm\) 4.9** \\  & N\(-\) & 14.7 \(\pm\) 1.0 & 40.1 \(\pm\) 2.6 & 44.0 \(\pm\) 2.9 & 51.9 \(\pm\) 2.6 & 58.2 \(\pm\) 5.2 & 77.3 \(\pm\) 5.2 & **80.7 \(\pm\) 2.6** \\ \hline \multirow{2}{*}{L4} & N+ & 19.2 \(\pm\) 1.0 & 32.7 \(\pm\) 2.6 & 45.2 \(\pm\) 3.9 & 71.1 \(\pm\) 5.1 & 94.3 \(\pm\) 6.8 & 119.1 \(\pm\) 10.3 & **130.4 \(\pm\) 2.9** \\  & N\(-\) & 7.9 \(\pm\) 1.0 & 23.2 \(\pm\) 2.0 & 27.7 \(\pm\) 2.0 & 39.5 \(\pm\) 2.6 & 54.8 \(\pm\) 4.9 & 77.3 \(\pm\) 3.5 & **89.2 \(\pm\) 6.0** \\ \hline \multirow{2}{*}{L5} & N+ & 39.0 \(\pm\) 1.7 & 138.9 \(\pm\) 3.4 & 247.3 \(\pm\) 19.5 & 287.9 \(\pm\) 1.7 & 358.5 \(\pm\) 2.6 & 394.6 \(\pm\) 29.4 & **501.4 \(\pm\) 25.6** \\  & N\(-\) & 18.1 \(\pm\) 1.0 & 37.3 \(\pm\) 1.7 & 47.4 \(\pm\) 1.7 & 58.7 \(\pm\) 1.9 & **84.1 \(\pm\) 2.6** & 83.6 \(\pm\) 2.6 & 76.8 \(\pm\) 6.9 \\ \hline \multirow{2}{*}{L6} & N+ & 7.3 \(\pm\) 1.0 & 14.1 \(\pm\) 1.0 & 14.7 \(\pm\) 1.0 & 20.3 \(\pm\) 1.7 & 22.0 \(\pm\) 1.7 & 24.3 \(\pm\) 1.9 & **27.7 \(\pm\) 2.6** \\  & N\(-\) & 7.9 \(\pm\) 1.0 & 19.8 \(\pm\) 1.0 & 21.5 \(\pm\) 2.0 & 27.1 \(\pm\) 1.7 & 43.5 \(\pm\) 3.5 & **57.6 \(\pm\) 3.4** & 48.6 \(\pm\) 1.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Biomass production (mg/L) by isolated cyanobacterial strains. The biomass production by the strains cultivated in BG11 N+ and BG11 N\(-\) media was measured at seven-day intervals. The highest biomass produced by each strain in the appropriate medium is marked with boldface.