Table 1 Assignment of NMR peaks 1–17 indicated on the spectrum in Fig. 3
From: Recalcitrant carbohydrates after enzymatic hydrolysis of pretreated lignocellulosic biomass
Peak number | Chemical group | 13C chemical shift (ppm) |
|---|---|---|
1 | Aliphatic lignin carbons not bound to oxygen | 32.5 |
2 | Aryl methoxyl carbons of lignin | 56.2 |
3 | C6 carbon of non-crystalline/amorphous cellulose, C6 carbon of hemicelluloses, OCγH2 carbons of lignin | 62.5 |
4 | C6 carbon of crystalline cellulose | 64.8 |
5 | C2,3,5 of cellulose, OCαH2 carbons of lignin | 72.5 |
6 | C2,3,5 of cellulose and hemicelluloses | 74.4 |
7 | C4 carbon of non-crystalline cellulose and hemicelluloses, OCβH2 carbons of lignin | 83.5 |
8 | C4 carbon of crystalline cellulose | 87.9 |
9 | C1 carbon of hemicelluloses | 101.8 |
10 | C1 carbon of cellulose | 105.0 |
11 | C2 and C6 aromatic carbons of syringyl and C5 and C6 aromatic carbons of guaiacyl in lignin | 110.0–115.0 |
12 | C2 of aromatic carbons guaiacyl in lignin | 126.6 |
13 | C1 and C4 aromatic carbons of syringyla | 136.9 |
14 | C3 and C5 aromatic carbons of syringyla and C1 and C4 aromatic carbons of guaiacyl in lignin | 148.0 |
15 | C3 and C5 aromatic carbons of syringylb in lignin | 153.5 |
16 | Carboxyl groups of lignin | 163.0–180.3 |
17 | Carboxyl groups of hemicelluloses | 173.6 |