Table 3 Structures and isolations of biological lignin, and corresponding pyrolytic behaviors

Softwood (Fir), hardwood (Eucalyptus), non-wood (moso-bamboo)

Industrial cellulase (CMCase)

Enzymatic treatment (hydrolysis) of biomass using CMCase at 40 °C for 48 h, followed by lignin collection via centrifugation and purification via mild acidolysis in dioxane/acidified water (0.01 mol/L HCl, 85:15, v:v) at 87 °C

Softwood/hardwood/non-wood EMAL lignin (> 50%)

Softwood EMAL lignin: G/H-type lignin with G (unit) = 91.2%, H (unit) = 2.8%, β-O-4 = 56.1%, α-O-4 and β-5 = 19.0%, β–β = 5.3%, β-1 = 2.9%

Hardwood/non-wood EMAL lignin: G/S/H-type lignin with G (unit) = 24.7/36.1%, S (unit) = 54.6/42.9%, H (unit) 1.5/21.0%, β-O-4 = 36.3/38.7%, α-O-4 and β-5 = 4.4/5.2%, β–β = 9.6/6.0%, β-1 = 2.0/0%

RT-300, 400, 500, 600 °C^a

800 °C^b—char: ~ 30%

300 °C^b: softwood EMAL lignin (coniferyl alcohol, sinapyl alcohol); 400 °C^b: hardwood EMAL lignin (coniferyl alcohol, sinapyl alcohol); 400 °C^b: non-wood EMAL lignin (4-vinylphenol, 4-vinylguaiacol, 4-vinylsringol)

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Ginkgo, poplar

White-rot fungus Physisporinus vitreus

Lignin isolated from biomass using Björkman method and modified by white-rot fungus at 30 °C and 150 rpm for 48 h

Ginkgo lignin-laccase, poplar lignin-laccase

Ginkgo lignin-laccase, poplar lignin-laccase: G/H-type lignin with acid soluble lignin (ASL) = 0.32/0.29%, Klason lignin = 97.26/97.05%, carbohydrates = 1.18/1.32%, ash = 0.38/0.41%, C = 59.98/58.89%, H = 6.01/5.57%, N = 0.43/0.15%, O = 33.32/35.21%, S = 0.26/0.18%, O/C (molar ratio) = 0.42/0.45, H/C (molar ratio) = 1.20/1.13, methoxy = 11.17/15.68%

RT-400, 600, 800 °C^c

600 °C (exp.)^c—gas/oil/char: Ginkgo lignin-laccase (13.8/14.5/43.3%), poplar lignin-laccase (15.5/11.4/40.7%)

600 °C (exp.)^c: Ginkgo lignin-laccase (2-methoxy-phenol, vanillin2-methoxy-4-methyl-phenol), poplar lignin-laccase (2,6-dimethoxy-phenol, 2-methoxy-phenol, isoeugenol)

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Four technical lignin [sugarcane bagasse steam explosion (SE), sugarcane bagasse soda-anthraquinone (SAQ), sodium lignosulfonate from eucalyptus (NaE) and sodium lignosulfonate from a mixture of eucalyptus and pine wood (NaPE)]

Lignin peroxidase (LiP), quinone reductase (OR)

Lignin treated by LiP and OR in sodium tartrate buffer (pH 3.0) at 25 °C for 24 h

SE-Lignin, SAQ-Lignin, NaE-Lignin, NaPE-Lignin

SE-Lignin, SAQ-Lignin, NaE-Lignin, NaPE-Lignin: G/S/H-type lignin with M_w = 10,126/6087/10,833/9023 g/mol, M_n = 800/1112/3165/4351 g/mol, Ð^e = 12.7/5.5/3.4/2.1

RT-550 °C^d

550 °C^d—gas/oil/char: SE-E-Lignin (8.8/47.4/43.8%), SAQ-E-Lignin (22.0/40.6/37.3%), NaE-E-Lignin (21.2/27.5/51.3%), NaPE-E-Lignin (36.4/19.8/43.8%)

550 °C^e: SE-Lignin, SAQ-Lignin, NaE-Lignin (phenol), NaPE-Lignin (guaiacol)

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Bamboo

White-rot fungus Echinodontium taxodii

Enzymatic hydrolysis performed in sodium acetate buffer (pH = 4.8) at 48 °C for 3 days, and lignin isolated by centrifugation

Lignin from enzymatic treated EHRL (86.4%)

G/S-type lignin with G/S (unit ratio) = 0.49, and with the decreasing content of β-O-4 structure

RT-600 °C^a

1100 K^f-char: 31.64, 32.18, 33.04% at 40, 20, 10 K/min

600 °C^a: 2,3-dihydrobenzofuran, syringol, vanillic acid

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