Solid acid enhanced ionic liquid (IL) pretreatment is a recyclable, environmentally benign and cost effective novel method for boosting the yield of sugars from lignocellulosic biomass. To unravel the chemical and supramolecular structural changes of lignin after pretreatment, IL-acid lignin (ILAL) and subsequent residual cellulolytic enzyme lignin (RCEL) were isolated from Arundo donax Linn. The structural features were compared with the corresponding milled wood lignin (MWL). Results indicated that the pretreatment caused loss of β-O-4′, β-β', β-1' linkages and formation of condensed structures in lignin. A preferential breakdown of G-type lignin was observed, evidenced by increased S/G ratio revealed by 2D HSQC NMR analysis. It was determined that the depolymerisation of β-O-4′ linkage, lignin re-condensation, and cleavage of ferulate-lignin ether linkages were took place. Moreover, a simulation module was first developed to define the morphological changes in lignin. MWL appeared as tree branch like aggregates, consisting of oblate ellipsoid-shaped monomers with different sizes. After the pretreatment, the supramolecular organization was completely destroyed and transformed into monodisperse monomers with some collapse present on monomer surfaces. These modifications contributed to reduction in molecular weight and lower maximum decomposition temperature of ILAL relative to MWL. The results presented will contribute to better understanding of native recalcitrant and facilitate the design of more effective deconstruction strategies for biorefineries.

Chemical and supramolecular structural modifications in lignin during acid catalyzed ionic liquid pretreatment: A case study of Arundo donax linn

251st National Meeting (2016)

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