INVESTIGATOR(S): Ralph, J. (Collaborators: Lu, F; Sundberg, B.; Mansfield, S.; others)
INSTITUTION: U.S. Dairy Forage Research Center, USDA-Agricultural Research Service
NON-TECHNICAL SUMMARY: In wide-ranging research aimed at altering plant cell wall characteristics, by conventional breeding or modern genetic methods, one of the biggest problems is in delineating the effects on the cell wall. Plant cell walls are a complex conglomerate of a variety of polysaccharides and lignin. Each component alone is complex, and their interactions are only poorly characterized and understood. The most common approach has been to isolate and purify components and to characterize them in detail using a variety of methods. Such studies will always be necessary. As studies in which lignin-biosynthetic pathway enzymes were targeted have made abundantly clear, simple compositional analysis is not sufficient. Some plants with only minor compositional changes have drastically altered chemical structure that belies the important alterations that can be made in processes ranging from natural digestibility in ruminant animals to industrial chemical pulping.
How can the structural components of the cell wall be readily characterized? Although other methods have their place, and can be more rapid (e.g. NIR), the difficulty in interpretation of some spectral methods, or the destruction of structure by chemical methods, assures that key features of cell walls benefiting, for example, biomass production and conversion are lost. A promising recent approach is the dissolution of the whole cell wall and NMR analysis. We intend to extend the methodologies to provide rapid structural profiling of plant materials, aiming for a "screening rate" of 20-30 samples per day. Such methodology will be useful to plant researchers worldwide.
OBJECTIVES: To provide the plant cell wall and biomass research communities with improved methods for polysaccharide and lignin structural profiling, based on complete cell wall solubilization and NMR. The aim is to develop and streamline procedures to allow 20-30 samples per day to be profiled.
APPROACH: The following improvements to the Dissolution/NMR method will be sought: a. Provide the necessary database, via model compounds and isolated components, to characterize component polysaccharides and lignins in whole-cell-wall mixtures. b. Optimize milling conditions for the various biomass sample types and seek alternative solutions that require less rigorous milling. c. Attempt to develop improved rapid dissolution methods that can be performed directly in the NMR tube; determine solvent systems that do not interfere with the correlation contours from polysaccharide and lignin components. d. Develop NMR methods that allow the crucial HSQC NMR spectra to be acquired in under 1 hour (on the whole cell wall sample). e. Develop methods for databasing and quantifying the 2D NMR cell wall spectra. f. With collaborators, attempt to develop chemometrics methods that can be applied to 2D NMR data.
KEYWORDS: lignin; plant chemistry; plant structure, polysaccharide, digestibility, chemical pulping,plant cell wall, NMR.
Name: Ralph, J.