Table 2.
Relative molar abundances of lignin markers from Py-GC/MS of eucalypt wood treated with laccase-mediator, laccase alone and control
| Compound | Control | Laccase only | Laccase-mediator |
|---|---|---|---|
| Guaiacol (G) |
4.4 |
4.8 |
6.4 |
| 4-methylguaiacol (G-CH3) |
2.6 |
2.0 |
1.2 |
| 4-ethylguaiacol (G-CH2-CH3) |
1.0 |
1.2 |
1.2 |
| 4-vinylguaiacol (G-CH = CH2) |
4.0 |
3.5 |
2.9 |
| Eugenol (G-CH2-CH = CH2) |
0.9 |
0.8 |
0.5 |
| Syringol (S) |
19.2 |
21.7 |
32.0 |
|
cis-isoeugenol (G-CH = CH-CH3) |
0.7 |
0.5 |
0.3 |
|
trans-isoeugenol (G-CH = CH-CH3) |
4.0 |
3.6 |
2.0 |
| 4-methylsyringol (S-CH3) |
7.5 |
7.2 |
5.0 |
| Vanillin (G-CHO) |
1.3 |
1.0 |
0.7 |
| 4-ethylsyringol (S-CH2-CH3) |
3.5 |
3.8 |
5.3 |
| Acetovanillone (G-CO-CH3) |
0.7 |
0.9 |
1.1 |
| 4-vinylsyringol (S-CH = CH2) |
13.3 |
12.4 |
12.3 |
| Guaiacylacetone (G-CH2-CO-CH3) |
0.5 |
0.5 |
0.5 |
| 4-allylsyringol (S-CH2-CH = CH2) + 4-propylsyringol (S-CH2-CH2-CH3) |
4.3 |
4.1 |
3.6 |
|
cis-propenylsyringol (S-CH = CH-CH3) |
2.6 |
2.3 |
1.8 |
|
trans-propenylsyringol (S-CH = CH-CH3) |
14.4 |
12.8 |
10.2 |
| Syringaldehyde (S-CHO) |
5.8 |
4.5 |
2.5 |
| Homosyringaldehyde (S-CH2-CHO) |
0.0 |
1.1 |
0.9 |
| Acetosyringone (S-CO-CH3) |
3.6 |
5.0 |
4.9 |
| Syringylacetone (S-CH2-CO-CH3) |
2.2 |
2.2 |
2.3 |
| Propiosyringone (S-CO-CH2-CH3) |
0.7 |
0.8 |
0.6 |
| Dihydrosinapyl alcohol (S-CH2-CH2-CH2OH) |
0.7 |
0.8 |
0.5 |
|
trans-sinapyl alcohol (S-CH = CH-CH2OH) |
0.8 |
0.2 |
0.3 |
|
trans-sinapaldehyde (S-CH = CH-CHO) |
1.0 |
2.3 |
1.0 |
| C6-C0-2/C6-C3 ratio |
2.0 |
2.2 |
3.2 |
| Syringyl-to-guaiacyl ratio | 4.0 | 4.3 | 4.9 |
Main lignin-derived compounds (lignin markers) from Py-GC/MS of eucalypt wood treated with M. thermophila laccase (50 U · g-1) and the mediator methyl syringate (3%) in a sequence including four enzymatic treatments and four alkaline peroxide extractions compared with a control without enzyme, and a treatment with laccase alone. Methyl syringate was also recovered among the Py-GC/MS products from the laccase and methyl syringate sample (amounting to 8% of the listed lignin-derived markers). The ratio between lignin markers with reduced side chains (C6-C0-2) and phenylpropane (C6-C3) markers, as well as the syringyl-to-guaiacyl ratio, are also indicated.