Two-Dimensional 1H-Nuclear Magnetic Resonance Relaxometry for Understanding Biomass Recalcitrance

Abstract

Low-field nuclear magnetic resonance (LFNMR) relaxometry examines the influence of the local environments within porous materials on the responses of the water-associated 1H to magnetic fields, yielding information on the chemical and physical surroundings of the water. 1D NMR relaxometry has been used to examine the relationship between water constraint within lignocellulosic biomass microstructure and its enzymatic digestibility; however, the effect of physical confinement and magnetic dephasing by the local chemistry could not be decoupled. This limitation is overcome by two-dimensional T1T2 1H NMR relaxometry, where simultaneously probing the spin–lattice and spin–spin relaxation times of water 1H resolves physical and chemical contributions to relaxation times of unique water environments within the sample. 2D T1T2 relaxation revealed four water environments in Norway spruce assigned to lumen and cell wall water based on water mobility in the pools. Sulfur dioxide (SO2) pretreatment of the spruce eli...