文献类型：期刊文献

英文题名：An uncondensed lignin depolymerized in the solid state and isolated from lignocellulosic biomass: a mechanistic study

作者：Li, Ning[1] Li, Yanding[1,2] Yoo, Chang Geun[1,3,4] Yang, Xiaohui[1,5] Lin, Xuliang[1,6] Ralph, John[1,2] Pan, Xuejun[1]

第一作者：Li, Ning

通信作者：Pan, XJ[1]

机构：[1]Univ Wisconsin, Dept Biol Syst Engn, Madison, WI 53706 USA;[2]Univ Wisconsin, Dept Biochem, Madison, WI 53706 USA;[3]Oak Ridge Natl Lab, BioEnergy Sci Ctr, Oak Ridge, TN 37831 USA;[4]Oak Ridge Natl Lab, Biosci Div, Oak Ridge, TN 37831 USA;[5]Chinese Acad Forestry, Inst Chem Ind Forestry Prod, Nanjing 210042, Jiangsu, Peoples R China;[6]Guangdong Univ Technol, Sch Chem Engn & Light Ind, Guangzhou 511400, Guangdong, Peoples R China

年份：2018

卷号：20

期号：18

起止页码：4224-4235

外文期刊名：GREEN CHEMISTRY

收录：;Scopus(收录号：2-s2.0-85053773361);WOS:【SCI-EXPANDED(收录号:WOS:000445773700019)】；

基金：The financial support from the National Science Foundation (NSF) (CBET 1159561), the U.S. Department of Agricultural (USDA) National Institute of Food and Agriculture, and the McIntire Stennis project (1006576) are acknowledged. Dr Gaojin Lyu kindly provided the beta-ether lignin model compound used in this study. The NMR analysis was conducted in the Magnetic Resonance Facility in the Chemistry Department at the University of Wisconsin-Madison. Ning Li would like to thank the China Scholarship Council (CSC) for partially supporting his PhD study at the University of Wisconsin-Madison. Yanding Li and John Ralph were funded by the DOE Great Lakes Bioenergy Research Center (DOE BER Office of Science DE-SC0018409).

语种：英文

摘要：This study demonstrated that lignin could be efficiently depolymerized in the solid state with minimal condensation and separated from biomass with high purity by dissolving and hydrolyzing cellulose and hemicelluloses, using an acidic lithium bromide trihydrate (ALBTH) system under mild conditions (with 40 mM HCl at 110 degrees C). The ALBTH lignins isolated from biomass sources representing the three plant classes (hardwoods, softwoods, and grasses) contained abundant uncondensed moieties (i.e., Hibbert's ketones and benzodioxanes). The benzodioxane structure was identified and confirmed for the first time in an acid-depolymerized lignin. Reactions using lignin model compounds (LMCs, guaiacylglycerol-beta-guaiacyl ether and various aromatic monomers) confirmed the formation of the uncondensed moieties and revealed the synergy between LiBr and acid in inducing the crucial intermediate benzyl carbocations, which then led to cleavage of the beta-O-4-aryl ether bonds to produce Hibbert's ketones, demethylation to produce benzodioxanes, and condensation reactions. Unlike in the LMC reactions, the condensation of the real lignin in biomass under ALBTH conditions was greatly diminished, possibly due to lignin remaining in the solid state, limiting its mobility and accessibility of the benzyl carbocation to the electron-rich aromatic sites for condensation. Preliminary results indicated that, because of its uncondensed nature, the ALBTH lignin was a good lignin feedstock for hydrogenolysis. This study provided a new approach to effectively isolate depolymerized lignin from lignocellulose in a less condensed form for boosting its downstream valorization.