Nuclear Magnetic Resonance and Small-Angle Neutron Analysis of Native and Deuterium Enriched Biomass for the Detailed Analysis of Lignocellulosic Breakdown

In an effort to better understand the complex mechanisms of lignocellulose recalcitrance and breakdown during pretreatment and enzymatic hydrolysis various potential energy crops have been enriched with deuterium for small-angle neutron scattering (SANS) and nuclear magnetic resonance (NMR) studies.   Laboratory grown deuterium-labeled plants including: duckweed, switchgrass, rye grass, and a commercially deuterated kale, were analyzed for deuterium incorporation levels and distribution by two novel applications of NMR.  The first methodology uses solid state NMR and the second is based on whole plant cell wall dissolution by an ionic liquid followed by liquids ²H/¹H NMR both verifying the control deuterated kale showed 33-35% deuterium incorporation.  Preliminary SANS results on fully protonated biomass to characterize morphological changes in switchgrass during dilute acid pretreatment demonstrate an increase in the cross-sectional radius of the crystalline cellulose fibril.  This change is accompanied by the formation of R_g ~ 135 Å lignin aggregates.