Effect of in Vivo Deuteration on Structure of Switchgrass Lignin

Biomass deuteration is an effective engineering method that can be used to provide key insights into understanding of biomass recalcitrance and the complex biomass conversion process. In this study, production of deuterated switchgrass was accomplished by growing the plants in 50% D₂O under hydroponic conditions in a perfusion chamber. Cellulolytic enzyme lignin was isolated from deuterated switchgrass, characterized by Fourier transform infrared (FTIR), gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR) and compared with its protiated control sample to determine the effect of in vivo deuteration on the chemical structure of lignin. FTIR results showed that D₂O can be taken up by the roots and transported to the leaves, and deuterium was subsequently incorporated into hydroxyl and alkyl groups in the plant and its lignin through photosynthesis. According to GPC results, deuterated lignin had slightly higher molecular weight, presumably due to isotope effects. ³¹P and heteronuclear single quantum coherence (HSQC) NMR results revealed that lignin in the deuterated biomass preserved its native physicochemical characteristics. The conserved characteristics of the deuterated lignin show its great potential applications for structural and dynamic studies of lignocellulose by techniques such as neutron scattering.