Abstract
Aqueous ionic liquids (ILs) have received increasing interest because of their high efficacy in fractionating and pretreating lignocellulosic biomass while at the same time mitigating several challenges associated with IL pretreatment such as IL viscosity, gel formation during pretreatment, and the energy consumption and costs associated with IL recycling. This study investigated the fate of lignin, its structural and compositional changes, and the impact of lignin modification on the deconstruction of cell wall compounds during aqueous IL (10% w/w cholinium lysinate) pretreatment of wild-type and engineered switchgrass. The 4CL genotype resulting from silencing of 4-coumarate:coenzyme A ligase gene (Pv4CL1) had a lower lignin content, relatively higher amount of hydroxycinnamates, and higher S/G ratio and appeared to be less recalcitrant to IL pretreatment likely due to the lower degree of lignin branching and more readily lignin solubilization. The results further demonstrated over 80% of lignin dissolution from switchgrass into the liquid fraction under mild conditions while the remaining solids were highly digestible by cellulases. The soluble lignin underwent partial depolymerization to a molecular weight around 500-1000 Da. 1H-13C HSQC NMR results demonstrated that the variations in lignin compositions led to different modes of lignin dissolution and depolymerization during pretreatment of engineered switchgrass. These results provide insights into the impact of lignin manipulation on biomass fractionation and lignin depolymerization and lead to possible ways toward developing a more selective and efficient lignin valorization process based on aqueous IL pretreatment technology.
| Original language | English |
|---|---|
| Pages (from-to) | 6612-6623 |
| Number of pages | 12 |
| Journal | ACS Sustainable Chemistry and Engineering |
| Volume | 6 |
| Issue number | 5 |
| DOIs | |
| State | Published - May 7 2018 |
Funding
We acknowledge the National Science Foundation under Cooperative Agreements 1355438 and 1632854 for partially supporting this research. The information reported in this paper (18-05-039) is part of a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director. We thank Novozymes for providing enzyme samples. Oak Ridge National Laboratory is managed by UT-Battelle, LLC under Contract DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). This work was partially supported by the BioEnergy Science Center (BESC) and the Center for Bioenergy Innovation (CBI). The BESC and CBI are U.S. DOE Bioenergy Research Centers supported by the Office of Biological and Environmental Research in the DOE Office of Science. The views and opinions of the authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. The Virginia Tech work was partially supported by USDA-NIFA Grant 2011-67009-30133 and by a Virginia Tech CALS integrative grant and the Virginia Agricultural Experiment Station (VA135872).We would like to thank Dr. Chang Geun Yoo for assisting with the preparation of the 2D NMR figures. We acknowledge the National Science Foundation under Cooperative Agreements 1355438 and 1632854 for partially supporting this research. The information reported in this paper (18-05-039) is part of a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director. We thank Novozymes for providing enzyme samples. Oak Ridge National Laboratory is managed by UT-Battelle, LLC under Contract DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). This work was partially supported by the BioEnergy Science Center (BESC) and the Center for Bioenergy Innovation (CBI).TheBESC and CBI areU.S. DOE Bioenergy Research Centers supported by the Office of Biological and Environmental Research in the DOE Office of Science.
| Funders | Funder number |
|---|---|
| BioEnergy Science Center | |
| National Science Foundation | 1355438, 1632854 |
| U.S. Department of Energy | |
| U.S. Department of Agriculture | 2011-67009-30133 |
| Office of Science | |
| Biological and Environmental Research | |
| Oak Ridge National Laboratory | DE-AC05-00OR22725 |
| Kentucky Agricultural Experiment Station | |
| Virginia Agricultural Experiment Station, Virginia Polytechnic Institute and State University | VA135872 |
| Center for Bioenergy Innovation | |
| UT-Battelle | |
| National Science Foundation | 18-05-039 |
Keywords
- Engineered switchgrass
- Ionic liquid
- Lignin
- Pretreatment
