Abstract
The complex structure of plant cell walls resists chemical or biological degradation, challenging the breakdown of lignocellulosic biomass into renewable chemical precursors that could form the basis of future production of green chemicals and transportation fuels. Here, experimental and computational results reveal that the effect of the tetrahydrofuran (THF)-water cosolvents on the structure of lignin and on its interactions with cellulose in the cell wall drives multiple synergistic mechanisms leading to the efficient breakdown and fractionation of biomass into valuable chemical precursors. Molecular simulations show that THF-water is an excellent "theta" solvent, such that lignin dissociates from itself and from cellulose and expands to form a random coil. The expansion of the lignin molecules exposes interunit linkages, rendering them more susceptible to depolymerization by acid-catalyzed cleavage of aryl-ether bonds. Nanoscale infrared sensors confirm cosolvent-mediated molecular rearrangement of lignin in the cell wall of micrometer-thick hardwood slices and track the disappearance of lignin. At bulk scale, adding dilute acid to the cosolvent mixture liberates the majority of the hemicellulose and lignin from biomass, allowing unfettered access of cellulolytic enzymes to the remaining cellulose-rich material, allowing them to sustain high rates of hydrolysis to glucose without enzyme deactivation. Through this multiscale analysis, synergistic mechanisms for biomass deconstruction are identified, portending a paradigm shift toward first-principles design and evaluation of other cosolvent methods to realize low cost fuels and bioproducts.
| Original language | English |
|---|---|
| Pages (from-to) | 12545-12557 |
| Number of pages | 13 |
| Journal | Journal of the American Chemical Society |
| Volume | 141 |
| Issue number | 32 |
| DOIs | |
| State | Published - Aug 14 2019 |
Funding
We acknowledge support from the Office of Biological and Environmental Research in the Department of Energy (DOE) Office of Science through the BioEnergy Science Center (BESC) and the Center for Bioenergy Innovation (CBI) at Oak Ridge National Laboratory. The award of a fellowship to the lead author by the National Center for Sustainable Transportation made his participation in this project possible. We also acknowledge the support from the Genomic Science Program, Office of Biological and Environmental Research, U.S. Department of Energy (contract FWP ERKP752), and funding from the Southeastern Regional Sun Grant Center at the University of Tennessee through a grant provided by the U.S. Department of Agriculture (award number 2014-38502-22598). This research used resources of the Oak Ridge Leadership Computing Facility under an INCITE award (contract FWP DE-AC05-00OR22725) and the Compute and Data Environment for Science (CADES) resources at the Oak Ridge National Laboratory. We also acknowledge the Center for Environmental Research and Technology (CE-CERT) of the Bourns College of Engineering at University of California Riverside for providing the facilities and the Ford Motor Co. for funding the Chair in Environmental Engineering that facilitates projects such as this one.