Modification of the lignin structure during alkaline delignification of eucalyptus wood by kraft, soda-AQ, and soda-O2 cooking

11 páginas.-- 5 figuras.-- 4 tablas.-- 50 referencias.-- Supporting Information The general conditions for the kraft, soda-AQ, and soda-O2 alkaline cooking of eucalyptus feedstock, are shown in Table S1. The identification and relative molar abundance of the compounds identified in the Py-GC/MS of MWL from eucalyptus wood, and residual and black liquor lignins from kraft, soda-AQ,and soda-O2 pulping at different kappa numbers, are listed in Table S2. This material is available free of charge via the Internet at http://pubs.acs.org/doi/suppl/10.1021/ie401364dThe modification of the lignin structure of an eucalyptus feedstock during alkaline delignification by kraft, soda-AQ, and soda-O2 cooking processes has been investigated by different analytical techniques (size exclusion chromatography (SEC), pyrolysis gas chromatography-mass spectroscopy (Py-GC/MS), 1H-13C two-dimensional nuclear magnetic resonance (2D-NMR), and 31P NMR). The characteristics of the lignins were compared at different pulp kappa levels, and with the native lignin isolated from the wood. The structural differences between the kraft, soda-AQ, and soda-O2 residual lignins were more significant at earlier pulping stages. At the final stages, all the lignin characteristics were similar, with the exception of their phenolic content. Strong differences between lignins from pulps and cooking liquors were observed, including enrichment in guaiacyl units in pulp residual lignin and enrichment in syringyl units in black liquor lignin. A comparison of the alkaline cookings indicate that soda-O2 process produced higher lignin degradation and provided promising results as pretreatment for the deconstruction of eucalyptus feedstocks for subsequent use in lignocellulose biorefineries. © 2013 American Chemical Society.This study has been funded by the EU-Project LIGNODECO (No. KBBE-244362), the Spanish project (No. AGL2011-25379), and the CSIC project (No. 201040E075). Dr. Rencoret thanks the CSIC for a JAE-DOC contract in the program “Junta para la Ampliación de Estudios”, cofinanced by Fondo Social Europeo (FSE). Finally, we thank Suzano Papel e Celulose (Brazil) for providing the pulp and black liquor samples from the alkaline cooking experiments and the corresponding additional data.Peer Reviewe

Modification of the lignin structure of eucalypt feedstocks during chemical deconstruction by kraft, soda-AQ and soda-O2 processing

The modification of the lignin structure in an eucalypt feedstock after alkaline deconstruction by the kraft, soda-AQ and soda-O2 processes was assessed. For this purpose, the residual lignins isolated from the pulps at kappa levels 50, 35, 20 and 15 were analyzed by different analytical techniques, including 2D-NMR, 31P-NMR and SEC (size exclusion chromatography). In addition, dissolved lignins precipitated from the black liquors of the kraft and soda-AQ processes at kappa 20 and 15 were also analyzed. The distribution of the different lignin substructures in the residual lignins was similar to that in the native lignin, although with a drastic reduction in their content. This reduction was more evident in pulps with lower kappa number due to the more drastic pulping conditions.The research leading to these results has received funding from the European Community's Seventh Framework Programme FP7/2007-2013 under grant agreement no KBBE-2009-3-244362 LignoDeco (EU/Brazil co-operation). We thank Suzano Papel e Celulose (Brasil) for providing the pulps and the black liquors.Peer reviewe

Versatile peroxidase as a valuable tool for generating new biomolecules by homogeneous and heterogeneous cross-linking

9 páginas, 8 figuras, 2 tablas -- PAGS nros. 303-311The modification and generation of new biomolecules intended to give higher molecular-mass species for biotechnological purposes, can be achieved by enzymatic cross-linking. The versatile peroxidase (VP) from Pleurotus eryngii is a high redox-potential enzyme with oxidative activity on a wide variety of substrates. In this study, VP was successfully used to catalyze the polymerization of low molecular mass compounds, such as lignans and peptides, as well as larger macromolecules, such as protein and complex polysaccharides. Different analytical, spectroscopic, and rheological techniques were used to determine structural changes and/or variations of the physicochemical properties of the reaction products. The lignans secoisolariciresinol and hydroxymatairesinol were condensed by VP forming up to 8 unit polymers in the presence of organic co-solvents and Mn2+. Moreover, 11 unit of the peptides YIGSR and VYV were homogeneously cross-linked. The heterogeneous cross-linking of one unit of the peptide YIGSR and several lignan units was also achieved. VP could also induce gelation of feruloylated arabinoxylan and the polymerization of β-casein. These results demonstrate the efficacy of VP to catalyze homo- and hetero-condensation reactions, and reveal its potential exploitation for polymerizing different types of compoundsThis work has been carried out with funding from the EU FP7 project “Peroxicats” (KBBE-2010-4-265397), the Spanish Ministry of Science and Innovation (BIO2009-08446, PRI-PIBAR-2011-1402), and the project “Lignin Fibre” financed by the Academy of Finland (Grant number 133091)Peer reviewe