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Title: Chemical structure and heterogeneity differences of two lignins from loblolly pine as investigated by advanced solid-state NMR spectroscopy

Author
item Holtman, Kevin
item CHEN, N - Old Dominion University
item CHAPPELL, MARK - Us Army Corp Of Engineers (USACE)
item KADIA, J.F. - University Of British Columbia
item XU, L - James Madison University
item MAO, J - Old Dominion University

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2010
Publication Date: 9/22/2010
Citation: Holtman, K.M., Chen, N., Chappell, M.A., Kadia, J., Xu, L., Mao, J. 2010. Chemical structure and heterogeneity differences of two lignins from loblolly pine as investigated by advanced solid-state NMR spectroscopy. Journal of Agricultural and Food Chemistry. 58(18):9882-9892.

Interpretive Summary: In the use of lumber and underutilized biomass accurate techniques are required to characterize biomass that are not dependent on the pretreatment of the feedstock and that correlate to “real-world” milled samples. Advanced analytical techniques (solid-state NMR) were employed to investigate differences in chemical structure and heterogeneity between milled wood lignin (MWL) and residual enzyme lignin (REL). The advanced NMR techniques included 13C quantitative direct polarization, various spectral-editing techniques, and two-dimensional NMR. Results showed that the two lignins were quite similar to those of two milled woods obtained industrially. REL contained much more residual carbohydrates than MWL, showing that MWL extraction more successfully separated lignin from cellulose and hemicelluloses than REL extraction. This information can be used by the lumber and cellulose ethanol industries to best pretreat and analyze wood samples.

Technical Abstract: Advanced solid-state NMR was employed to investigate differences in chemical structure and heterogeneity between milled wood lignin (MWL) and residual enzyme lignin (REL). Wiley and conventional milled woods were also studied. The advanced NMR techniques included 13C quantitative direct polarization, various spectral-editing techniques, and two-dimensional 1H-13C heteronuclear correlation NMR with 1H spin diffusion. The 13C chemical shift regions between 110 and 160 ppm of two lignins were quite similar to those of two milled woods. REL contained much more residual carbohydrates than MWL, showing that MWL extraction more successfully separated lignin from cellulose and hemicelluloses than REL extraction; REL was also of higher COO, aromatic C-C, and condensed aromatics but of lower aromatic C-H. At a spin diffusion time of 0.55 ms, the magnetization was equilibrated through the whole structure of MWL lignin, but not through that of REL, indicating that REL is more heterogeneous than MWL.