Characterization of residual lignin after SO(2)-catalyzed steam explosion and enzymatic hydrolysis of Eucalyptus viminalis wood chips.
The lignin component found in both water insoluble (WI) and water and alkali insoluble (WIA) fractions derived from SO(2)-impregnated steam-exploded eucalyptus chips (SEE) was isolated and characterized. Dioxane lignins with a sugar content lower than 2% (w/w) were obtained after each material was treated with commercial cellulases. The C9 formulas of both SEE-WI and SEE-WIA dioxane lignins were C(9)H(6.83)N(0.04)O(2.24)(OCH(3))(1.21)(OH(aro))(0.56)(OH(ali))(0. 77) and C(9)H(8.65)N(0.29)O(1.97)(OCH(3))(0.90)(OH(aro))(0. 46)(OH(ali))(1.02), respectively. The weight-average molecular weight (M(w)) of the SEE-WI lignin corresponded to 3.85 kDa, whereas the SEE-WIA lignin had an M(w) of 3.66 kDa for the same polydispersity of 2.4. The SEE-WIA lignin was shown to be more thermally stable than the SEE-WI lignin, requiring temperatures in the range of 520 degrees C for complete degradation. FTIR and (1)H NMR analyses of both untreated and peracetylated lignin fractions showed that (a) the alkali insoluble lignin contained a relatively higher degree of substitution in aromatic rings per C9 unit and that (b) alkaline extraction removed lignin fragments containing appreciable amounts of phenolic hydroxyl groups.
Ramos
L P
LP
Centro de Pesquisa em Química Aplicada, Departamento de Química, Universidade Federal do Paraná, Curitiba, Brazil. lramos@quimica.ufpr.br
Mathias
A L
AL
Silva
F T
FT
Cotrim
A R
AR
Ferraz
A L
AL
Chen
C L
CL
D002480:Cellulase; D005052:Eucalyptus; D006358:Hot Temperature; D006868:Hydrolysis; D008031:Lignin / Q000032:analysis / Q000737:chemistry*; D010946:Plants, Medicinal; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013458:Sulfur Dioxide; D014934:Wood
D013458:Sulfur Dioxide; D008031:Lignin; D002480:Cellulase