2024-03-29T09:44:44Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/33032020-11-13T13:29:45Zcom_10261_15com_10261_6com_10261_86com_10261_1col_10261_268col_10261_339
Ibarra, David
Chávez Uribe, María Isabel
Rencoret, Jorge
Río Andrade, José Carlos del
Gutiérrez Suárez, Ana
Romero Sánchez, Javier
Camarero, Susana
Martínez, María Jesús
Jiménez-Barbero, Jesús
Martínez, Ángel T.
2008-03-25T15:52:05Z
2008-03-25T15:52:05Z
2007
Holzforschung 61(6): 634-646 (2007)
0018-3830
http://hdl.handle.net/10261/3303
10.1515/HF.2007.096
1437-434X
Modification of eucalypt pulp residual lignin in a totally chlorine free (TCF) bleaching sequence including a laccase-mediator stage, in combination with previous oxygen delignification and subsequent peroxide bleaching, was investigated and compared with a chemical TCF sequence. The enzymatic treatment resulted in a strong oxidative modification, as shown by lignin unit 13C2,6-1H2,6 correlations in HSQC 2D-NMR spectra and presence of oxidized pyrolysis markers. The frequency of inter-unit linkages in residual lignin was also modified, as shown by different side-chain 13C-1H correlations. Moreover, H2,6 correlations with side-chain carbons in HMBC spectra revealed the presence of Cα keto and carboxyl groups in lignin from the oxygen-delignified and especially from the enzymatically-treated pulp, together with normal (Cα-hydroxylated) lignin units. Moreover, the results obtained showed that most of this oxidatively-altered lignin is removed under the alkaline conditions used in the peroxide stage. In this way, the pulp kappa number decreased, and the final residual lignin was more structurally-related to that found before the oxidative stages (although with lower content of resinol structures, and higher presence of aryl-aryl ether structures and carboxyl-bearing terminal units). However, the action of hydrogen peroxide is required to attain the high brightness, over 91% ISO, found in final pulp after the enzyme-containing TCF sequence.
eng
openAccess
2D NMR
Enzymes
Eucalyptus globulus
FTIR
HMBC
HSQC
Laccase-mediator system
Paper pulp
Py-GC/MS
TCF bleaching
Structural modification of eucalypt pulp lignin in a totally chlorine free bleaching sequence including a laccase-mediator stage
artículo