Table 2.
Semi-quantitative HSQC NMR structural characterization of residual lignin in control and fungal-treated wheat straw after 7 weeks of growth
| Control | Cs1 | Cs12 | Pe3 | Pe6 | Le8 | Le10 | |
|---|---|---|---|---|---|---|---|
| Lignin subunits (%)a | |||||||
| H | 2 (6) | 3 (5) | 3 (6) | 3 (6) | 2 (6) | 2 (5) | 3 (5) |
| G | 52 (53) | 47 (49) | 42 (46) | 57 (57) | 53 (53) | 53 (54) | 57 (56) |
| Gox | 2 (1) | 11 (8) | 12 (9) | 2 (2) | 3 (3) | 6 (5) | 4 (3) |
| Gmod | 0 (0) | 3 (2) | 4 (3) | 0 (0) | 1 (1) | 0 (0) | 0 (0) |
| S | 37 (34) | 25 (26) | 25 (26) | 31 (30) | 32 (31) | 30 (29) | 29 (30) |
| Sox | 5 (4) | 10 (7) | 12 (9) | 6 (5) | 6 (5) | 6 (5) | 5 (4) |
| Smod | 2 (1) | 3 (2) | 2 (2) | 1 (1) | 1 (1) | 2 (2) | 1 (1) |
| S/G | 0.81 (0.72) | 0.62 (0.60) | 0.67 (0.64) | 0.65 (0.59) | 0.69 (0.64) | 0.63 (0.60) | 0.58 (0.59) |
| Hydroxycinnamates (%)b | |||||||
| p-Coumarate | 6 (5) | 5 (3) | 5 (3) | 5 (4) | 5 (4) | 5 (3) | 4 (3) |
| Ferulate | 21 (15) | 19 (14) | 18 (13) | 15 (12) | 15 (12) | 16 (13) | 17 (13) |
| Lignan (%)b | |||||||
| Tricin | 10 (7) | 11 (8) | 9 (7) | 6 (5) | 7 (5) | 8 (6) | 10 (8) |
| Lignin inter-unit linkages (%)c | |||||||
| β-O-4′ Aryl ethers | 43 (90) | 37 (93) | 32 (97) | 39 (90) | 39 (85) | 40 (86) | 40 (88) |
| Phenylcoumarans | 3 (6) | 2 (4) | 1 (2) | 3 (7) | 5 (11) | 4 (10) | 3 (7) |
| Resinols | 1 (3) | 1 (3) | 0 (1) | 1 (3) | 2 (4) | 2 (4) | 2 (4) |
| Total | 48 (100) | 40 (100) | 33 (100) | 43 (100) | 46 (100) | 46 (100) | 45 (100) |
Volume integration of cross peaks in the aliphatic region likely suffered from overlap with carbohydrates, especially after extensive delignification
Cs Ceriporiopsis subvermispora, Pe Pleurotus eryngii, Le Lentinula edodes
aPercentage of subunits (H +G +Gox + Gmod + S + Sox + Smod = 100) and in parenthesis (subunits + pCA(H) + FA(G) + T(S) = 100)
bPercentage vs aromatic units and subunits + pCA + FA + T (see subscript a)
cPercentage of inter-unit linkages vs total subunits and in parenthesis as percentage of total inter-unit linkages