Effect of thermochemical pretreatment on lignin alteration and cell wall microstructural degradation in Eucalyptus globulus: comparison of acid, alkali, and water pretreatments

Journal of Wood Science

Official Journal of the Japan Wood Research Society

Table 2 Yields of thioacidolysis monomers and lignin monomers [syringaldehyde (Sa) and vanillin (Va)] in the residual and solubilized fractions after pretreatment

Pretreatment	Residue					Solubilized fraction into supernatant water
	Weight (mg)	Thioacidolysis monomers				Weight^a (mg)	Lignin monomers				Thioacidolysis monomers				Yields^b of monomers in the supernatant (%)
		(μmol)					(μmol)				(μmol)
		S	G	S + G	S:G		Sa	Va	Sa + Va	Sa:Va	S	G	S + G	S:G
Untreated		6.42	1.83	8.25	78:22
1.0 % H₂SO₄	6.1	0.22	0.12	0.34	65:35	3.9	0.09	0.02	0.11	83:17	0.02	nd	0.02	100:0	1.7
Hot water	4.5	0.07	0.02	0.10	75:25	5.6	0.32	0.06	0.38	85:15	0.16	0.06	0.24	72:28	7.2
0.5 % NaOH	3.6	tr	tr	tr	–	6.4	1.23	0.28	1.51	81:19	0.01	tr	0.02	90:10	18.5

Yields of thioacidolysis monomers and Sa and Va are expressed as μmol per residual or solubilized wood (per each weight)
tr trace, nd not detected
^aWeight of solubilized fraction was calculated from subtracting the weight of residual wood from the initial weight (i.e., 10 mg)
^bThe yield of the sum of (Sa + Va) + (S + G) in the solubilized fraction and its percentage against the amounts of the thioacidolysis monomers recovered from the untreated wood (8.25 μmol)