Supramolecular Interactions in Secondary Plant Cell Walls: Effect of Lignin Chemical Composition Revealed with the Molecular Theory of Solvation.
Plant biomass recalcitrance, a major obstacle to achieving sustainable production of second generation biofuels, arises mainly from the amorphous cell-wall matrix containing lignin and hemicellulose assembled into a complex supramolecular network that coats the cellulose fibrils. We employed the statistical-mechanical, 3D reference interaction site model with the Kovalenko-Hirata closure approximation (or 3D-RISM-KH molecular theory of solvation) to reveal the supramolecular interactions in this network and provide molecular-level insight into the effective lignin-lignin and lignin-hemicellulose thermodynamic interactions. We found that such interactions are hydrophobic and entropy-driven, and arise from the expelling of water from the mutual interaction surfaces. The molecular origin of these interactions is carbohydrate-π and π-π stacking forces, whose strengths are dependent on the lignin chemical composition. Methoxy substituents in the phenyl groups of lignin promote substantial entropic stabilization of the ligno-hemicellulosic matrix. Our results provide a detailed molecular view of the fundamental interactions within the secondary plant cell walls that lead to recalcitrance.
†National Institute for Nanotechnology, 11421 Saskatchewan Drive NW, Edmonton, Alberta T6G 2M9, Canada.|‡Institute of Chemistry, University of Campinas, Caixa Postal 6154, Campinas CEP 13083-970, São Paulo, Brazil.
Rodrigo L
RL
Silveira
†National Institute for Nanotechnology, 11421 Saskatchewan Drive NW, Edmonton, Alberta T6G 2M9, Canada.|§Department of Mechanical Engineering, University of Alberta, 4-9 Mechanical Engineering Building, Edmonton T6G 2G8, Alberta, Canada.|∥Department of Chemical and Materials Engineering, University of Alberta, 9107 - 116 Street, Edmonton T6G 2V4, Alberta, Canada.
Stanislav R
SR
Stoyanov
†National Institute for Nanotechnology, 11421 Saskatchewan Drive NW, Edmonton, Alberta T6G 2M9, Canada.
Sergey
S
Gusarov
‡Institute of Chemistry, University of Campinas, Caixa Postal 6154, Campinas CEP 13083-970, São Paulo, Brazil.
Munir S
MS
Skaf
†National Institute for Nanotechnology, 11421 Saskatchewan Drive NW, Edmonton, Alberta T6G 2M9, Canada.|∥Department of Chemical and Materials Engineering, University of Alberta, 9107 - 116 Street, Edmonton T6G 2V4, Alberta, Canada.
Andriy
A
Kovalenko
D018533:Biomass; D002473:Cell Wall / Q000737:chemistry*; D008031:Lignin / Q000737:chemistry*; D008954:Models, Biological; D010944:Plants / Q000737:chemistry*; D012995:Solubility
D008031:Lignin
3D-RISM-KH molecular theory of solvation; biofuel; hemicellulose; hydrophobic interactions; plant biomass recalcitrance; solvation free energy