# Marine microalgae Biomolecules and Their Adhesion Capacity to _Salmonella enterica_ sv. Typhimurium
## 3 Results
### Extraction and Characterization of Polysaccharides from P. gyrans and P. lutheri

Table 2: Characteristic total volatile matter content (%) of the different stages for microalgal extracts at a heating rate of 10 \({}^{\circ}\)C\(\cdot\)min\({}^{-1}\). Figure 2: Thermogravimetric (**a,c**) and derivative thermogravimetric curves (**b,d**) of aqueous and alkaline fractions from _P. gyrans_ (GW-p, GW-s, GA-p, GA-s) and _P. lutheri_ (LW-p, LW-s, LA-p, LA-s) at a heating rate of 10 \({}^{\circ}\)C\(\cdot\)min\({}^{-1}\) under a nitrogen atmosphere. In the first stage of the decomposition process, ranging from 20-150 \({}^{\circ}\)C, a slight mass loss in the TG curves was observed (4.6%-10.1%) due to water loss (free and loosely bound water) and some light volatile compounds. By comparing the first stage in the DTG curves (Figure 2b,d), the results showed subtle differences in the peak temperatures between 41.8 and 70.6 \({}^{\circ}\)C. These differences might have been due to the location and intermolecular forces between water molecules and the carbonaceous matrix that influenced the water elimination, and consequently, the peak temperatures [35]. The second stage of decomposition, between 150 and 500 \({}^{\circ}\)C, represented the main devolatilization reaction, where most of the sample mass was released as volatile matter. This stage involved the decomposition of microalgae organic substances, including proteins and carbohydrates, present in all the studied fractions (Table 1). The percentages of volatile matter (Table 2) were between 55.6% and 66.1% of the initial mass, except for GW-p and LW-p, which showed higher values (78.7% and 72.8%, respectively). The GW-p and LW-p DTG curves showed one intense sharp peak, indicating a high mass-loss rate; however, for GW-p, the inflection point was observed at 310 \({}^{\circ}\)C, while for LW-p, the inflection point was at 277 \({}^{\circ}\)C. One peak was also distinguished in this stage for GW-s at 264 \({}^{\circ}\)C. These differences in the thermal profiles may have been due to different chemical compositions, or differences in the linkage pattern of glucans present in these fractions [36; 37]. Stage 2 in the DTG curves (Figure 2b,d) of alkaline fractions (GA-p, GA-s, LA-p, LA-s) was complex as multiple overlapping peaks and wide shoulders were visible, in agreement with the chemical composition complexity observed for these fractions (Table 1). In the third stage, at temperatures higher than 500 \({}^{\circ}\)C, the carbonaceous materials retained in the solid residues were decomposed at a slow rate, resulting in the formation of a non-degradable residue. For nearly all the fractions, the percentage of non-degradable residue at 800 \({}^{\circ}\)C (Table 2) accounted for 6.5%-10.8% of the initial mass, with a higher value for LW-s and LA-s (16.5% and 20.1%, respectively). To elucidate the linkage pattern of the polysaccharides present in the aqueous fractions, GW-p and GW-s were submitted to methylation analysis, and the results are shown in Table 3. The methylation analysis of fraction GW-p revealed the major presence of the derivative 2,4,6-tri-\(O\)-methyl glucitol (90.0%), suggesting the presence of a main linear backbone constituted by 3-\(O\)-substituted glucopyranosyl units. In addition, the methylation analysis showed minor proportions of non-reducing terminal units, as well as 6- and 3,6-di-\(O\)-substituted glucopyranosyl units. The relative amount of nonbranched and disubstituted Glc\(p\) residues indicated one branching point for every \(\approx\)20 Glc\(p\) residues. In contrast, GW-s showed a highly branched structure, with non-reducing terminal, 3-, 6-, and 3,6-di-\(O\)-substituted glucopyranosyl units, indicating the presence of a (1\(\rightarrow\)3),(1\(\rightarrow\)6)-linked glucan, with one branching point every approximately four Glc\(p\) residues. Fractions were also examined using NMR spectroscopy. \({}^{1}\)H and \({}^{13}\)C NMR assignments were determined using spectral information from 1D and 2D NMR experiments and previously reported data.