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Pretreatment of wheat straw with laccase mediator system degrades lignin and improves saccharification

AuthorsRencoret, Jorge ; Pereira González, Antonio ; Río Andrade, José Carlos del ; Martínez, Ángel T. ; Gutiérrez Suárez, Ana
Issue Date19-Jun-2016
PublisherCSIC - Centro de Investigaciones Biológicas Margarita Salas (CIB)
Citation4th Symposium on Biotechnology applied to Lignocelluloses . Conference Book . pág. 85, (2016)
AbstractAgricultural by-products such as wheat straw are attractive feedstocks for the production of second generation bioethanol due to their high abundance [1]. Biofuel production from lignocellulosic material requires deconstruction of the cell-wall into individual polymers, and hydrolysis of the carbohydrates into monomeric sugars. In this context, one of the major factors causing biomass recalcitrance towards saccharification is correlated with the content and composition of lignin [2,3], whose presence hampers the enzymatic hydrolysis of carbohydrates. Hence, the purpose of this work is to study the ability of an enzymatic pretreatment based in the laccase-mediator system to remove/modify the lignin from wheat straw for improving saccharification. Pretreatment with Pycnoporus cinnabarinus laccase and 1-hydroxybenzotriazole (HBT) as mediator, followed by an alkaline peroxide extraction, removed up to 48% lignin from ground wheat straw. The lignin removal directly correlated with increases (~60%) in glucose yields after cellulase hydrolysis. The structural modifications occurring in the lignin polymer during the enzymatic pretreatment were studied ¿in situ¿ by two-dimensional nuclear magnetic resonance analysis (2D NMR) of the whole pretreated material at the gel-state [4]. The main lignin modifications included a reduction in the number of aliphatic side-chains involved in the major inter-unit linkages (ß-O-4' alkyl-aryl ethers and ß-5' phenylcoumarans) per aromatic lignin unit. Simultaneously, the removal of p-hydroxyphenyl, guaiacyl and syringyl lignin units and of p-coumaric and ferulic acids, as well as a moderate decrease of tricin units, was observed without a substantial change in the wood polysaccharide signals. Especially noteworthy was the formation of C¿-oxidized lignin units that indicates an oxidative depolymerisation mechanism.
Referencias: [1] Kim and Dale (2004) Global potential bioethanol production from wasted crops and crop residues. Biomass Bioenerg 26:361-375. [2] Studer et al. (2011) Lignin content in natural Populus variants affects sugar release. Proc Natl Acad Sci USA 108:6300-6305. [3] Li et al. (2010) Lignin monomer composition affects Arabidopsis cell-wall degradability after liquid hot water pretreatment. Biotechnol Biofuels 3:27. [4] Rencoret et al. (2009) HSQC-NMR analysis of lignin in woody (Eucalyptus globulus and Picea abies) and non-woody (Agave sisalana) ball-milled plant materials at the gel state. Holzforschung 63:691-698.
DescriptionComunicación presentada en el 4th Symposium on Biotechnology applied to Lignocelluloses . Conference Book . June 19-22, (2016) Madrid
Appears in Collections:(CIB) Comunicaciones congresos
(IRNAS) Comunicaciones congresos
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