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Table 2 Semi-quantitative HSQC NMR structural characterization of residual lignin in control and fungal-treated wheat straw after 7 weeks of growth

From: Mechanistic insight in the selective delignification of wheat straw by three white-rot fungal species through quantitative 13C-IS py-GC–MS and whole cell wall HSQC NMR

 

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)

  1. Volume integration of cross peaks in the aliphatic region likely suffered from overlap with carbohydrates, especially after extensive delignification
  2. Cs  Ceriporiopsis subvermispora, Pe  Pleurotus eryngii, Le  Lentinula edodes
  3. aPercentage of subunits (H +G  +Gox + Gmod + S + Sox + Smod = 100) and in parenthesis (subunits + pCA(H) + FA(G) + T(S) = 100)
  4. bPercentage vs aromatic units and subunits + pCA + FA + T (see subscript a)
  5. cPercentage of inter-unit linkages vs total subunits and in parenthesis as percentage of total inter-unit linkages