Performance of three delignifying pretreatments on hardwoods: hydrolysis yields, comprehensive mass balances, and lignin properties

Biotechnology for Biofuels

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[1] 0000 0001 2150 1785, grid.17088.36, DOE Great Lakes Bioenergy Research Center (GLBRC), Michigan State University, 48824, East Lansing, MI, USA;0000 0001 2150 1785, grid.17088.36, DOE Great Lakes Bioenergy Research Center (GLBRC), Michigan State University, 48824, East Lansing, MI, USA;0000 0001 2156 6108, grid.41891.35, Chemical & Biological Engineering Department, Montana State University, 59715, Bozeman, MT, USA;0000 0001 2150 1785, grid.17088.36, Department of Chemical Engineering and Materials Science, Michigan State University, 48824, East Lansing, MI, USA;0000 0001 1014 8699, grid.6926.b, Division of Sustainable Process Engineering, Luleå University of Technology, Luleå, Sweden;0000 0001 2150 1785, grid.17088.36, Department of Biochemistry & Molecular Biology, Michigan State University, 48824, East Lansing, MI, USA;0000 0001 2150 1785, grid.17088.36, DOE Great Lakes Bioenergy Research Center (GLBRC), Michigan State University, 48824, East Lansing, MI, USA;0000 0001 2150 1785, grid.17088.36, Department of Chemical Engineering and Materials Science, Michigan State University, 48824, East Lansing, MI, USA;0000 0001 2156 6108, grid.41891.35, Chemical & Biological Engineering Department, Montana State University, 59715, Bozeman, MT, USA;0000 0001 2222 1582, grid.266097.c, Department of Chemical and Environmental Engineering, University of California, Riverside, CA, USA;0000 0004 0446 2659, grid.135519.a, BioEnergy Science Center (BESC) and Center for Bioenergy Innovation (CBI), Oak Ridge National Laboratory, 37831, Oak Ridge, TN, USA;0000 0001 2231 4551, grid.184769.5, Joint BioEnergy Institute (JBEI), Lawrence Berkeley National Laboratory, 94720, Berkeley, CA, USA;

关键词: Pretreatment;    Cellulosic biofuels;    Lignin;    Aromatic monomers;   

DOI  :  10.1186/s13068-019-1546-0

来源: publisher

【 摘 要 】

BackgroundIn this work, three pretreatments under investigation at the DOE Bioenergy Research Centers (BRCs) were subjected to a side-by-side comparison to assess their performance on model bioenergy hardwoods (a eucalyptus and a hybrid poplar). These include co-solvent-enhanced lignocellulosic fractionation (CELF), pretreatment with an ionic liquid using potentially biomass-derived components (cholinium lysinate or [Ch][Lys]), and two-stage Cu-catalyzed alkaline hydrogen peroxide pretreatment (Cu-AHP). For each of the feedstocks, the pretreatments were assessed for their impact on lignin and xylan solubilization and enzymatic hydrolysis yields as a function of enzyme loading. Lignins recovered from the pretreatments were characterized for polysaccharide content, molar mass distributions, β-aryl ether content, and response to depolymerization by thioacidolysis.ResultsAll three pretreatments resulted in significant solubilization of lignin and xylan, with the CELF pretreatment solubilizing the majority of both biopolymer categories. Enzymatic hydrolysis yields were shown to exhibit a strong, positive correlation with the lignin solubilized for the low enzyme loadings. The pretreatment-derived solubles in the [Ch][Lys]-pretreated biomass were presumed to contribute to inhibition of enzymatic hydrolysis in the eucalyptus as a substantial fraction of the pretreatment liquor was carried forward into hydrolysis for this pretreatment. The pretreatment-solubilized lignins exhibited significant differences in polysaccharide content, molar mass distributions, aromatic monomer yield by thioacidolysis, and β-aryl ether content. Key trends include a substantially higher polysaccharide content in the lignins recovered from the [Ch][Lys] pretreatment and high β-aryl ether contents and aromatic monomer yields from the Cu-AHP pretreatment. For all lignins, the 13C NMR-determined β-aryl ether content was shown to be correlated with the monomer yield with a second-order functionality.ConclusionsOverall, it was demonstrated that the three pretreatments highlighted in this study demonstrated uniquely different functionalities in reducing biomass recalcitrance and achieving higher enzymatic hydrolysis yields for the hybrid poplar while yielding a lignin-rich stream that may be suitable for valorization. Furthermore, modification of lignin during pretreatment, particularly cleavage of β-aryl ether bonds, is shown to be detrimental to subsequent depolymerization.

【 授权许可】

CC BY