Overcoming cellulose recalcitrance in woody biomass for the lignin-first biorefinery

Biotechnology for Biofuels

Bruce R. Cooper¹  Xu Li²  Jeong Im Kim²  Lee Makowski³  Maureen C. McCann⁴  Nicholas C. Carpita⁴  Haibing Yang⁴  Varun Subramanyam⁵  Tânia M. Shiga⁵  Clint Chapple⁵  Hao Luo⁶  Mahdi M. Abu-Omar⁶  Baoyuan Liu⁶  Huaping Mo⁷  Richard Meilan⁸  Peter Rubinelli⁸  Jonathan C. Overton⁹  Ximing Zhang⁹  Nathan S. Mosier⁹  Bryon S. Donohoe^1,10 

[1] Bindley Bioscience Center, Purdue University;Department of Biochemistry, Purdue University;Department of Bioengineering, Northeastern University;Department of Biological Sciences, Purdue University;Department of Botany and Plant Pathology, Purdue University;Department of Chemistry and Biochemistry, University of California, Santa Barbara;Department of Chemistry, Purdue University;Department of Forestry and Natural Resources, Purdue University;Laboratory of Renewable Resource Engineering (LORRE), Department of Agricultural and Biological Engineering, Purdue University;National Renewable Energy Laboratory, Biosciences Center;

关键词: Cellulose;    Lignin;    Recalcitrance;    Catalysis;    Delignification;    Poplar;   

DOI  :  10.1186/s13068-019-1503-y

来源: DOAJ

【 摘 要 】

Abstract Background Low-temperature swelling of cotton linter cellulose and subsequent gelatinization in trifluoroacetic acid (TFA) greatly enhance rates of enzymatic digestion or maleic acid–AlCl3 catalyzed conversion to hydroxymethylfurfural (HMF) and levulinic acid (LA). However, lignin inhibits low-temperature swelling of TFA-treated intact wood particles from hybrid poplar (Populus tremula × P. alba) and results in greatly reduced yields of glucose or catalytic conversion compared to lignin-free cellulose. Previous studies have established that wood particles from transgenic lines of hybrid poplar with high syringyl (S) lignin content give greater glucose yields following enzymatic digestion. Results Low-temperature (− 20 °C) treatment of S-lignin-rich poplar wood particles in TFA slightly increased yields of glucose from enzymatic digestions and HMF and LA from maleic acid–AlCl3 catalysis. Subsequent gelatinization at 55 °C resulted in over 80% digestion of cellulose in only 3 to 6 h with high-S-lignin wood, compared to 20–60% digestion in the wild-type poplar hybrid and transgenic lines high in guaiacyl lignin or 5-hydroxy-G lignin. Disassembly of lignin in woody particles by Ni/C catalytic systems improved yields of glucose by enzymatic digestion or catalytic conversion to HMF and LA. Although lignin was completely removed by Ni/C-catalyzed delignification (CDL) treatment, recalcitrance to enzymatic digestion of cellulose from the high-S lines was reduced compared to other lignin variants. However, cellulose still exhibited considerable recalcitrance to complete enzymatic digestion or catalytic conversion after complete delignification. Low-temperature swelling of the CDL-treated wood particles in TFA resulted in nearly complete enzymatic hydrolysis, regardless of original lignin composition. Conclusions Genetic modification of lignin composition can enhance the portfolio of aromatic products obtained from lignocellulosic biomass while promoting disassembly into biofuel and bioproduct substrates. CDL enhances rates of enzymatic digestion and chemical conversion, but cellulose remains intrinsically recalcitrant. Cold TFA is sufficient to overcome this recalcitrance after CDL treatment. Our results inform a ‘no carbon left behind’ strategy to convert total woody biomass into lignin, cellulose, and hemicellulose value streams for the future biorefinery.

【 授权许可】

Unknown