Submitted to: American Chemical Society Symposium Series
Publication Type: Book / Chapter
Publication Acceptance Date: 2/18/1997
Publication Date: N/A
Citation: Interpretive Summary: Polysaccharides provide food and energy sources for microbes and ruminant animals. However, not all of the polysaccharides in plants are available for digestion. A major mechanism preventing full utilization is the plant's ability to cross-link its polysaccharides to other polysaccharides or to a much more inert substance, lignin, that is broken down only with great difficulty. Compounds called ferulates, present in quite small amounts in the plants cell walls, have a remarkable ability to effect this cross- linking. In the past, the mechanisms by which it accomplishes this were poorly understood. This review chapter presents the latest information on how ferulates on polysaccharides couple with other ferulates (to make diferulates) to cross-link the polysaccharides, and on how ferulates and diferulates become involved in the reactions that form lignin, tightly cross-linking the polysaccharides to lignin. Each of these pathways results sin polysaccharides that are less degradable and therefore less accessible as energy sources to, for example, ruminant animals. In addition to explaining how polysaccharide digestibility of plant cell walls is limited, the studies reviewed and explained in this Chapter suggest possibilities for improving the digestibility of plants. Such studies are at the heart of efforts to improve agricultural sustainability and maximize the benefits of our plant resources.
Technical Abstract: Ferulate polysaccharide esters in grasses enter into free-radical condensation reactions in the cell wall. By radical dimerization of ferulates, polysaccharide-polysaccharide cross-linking is effected. A range of diferulate isomers are produced, only one of which has been quantitated in the past. Diferulates have been underestimated by factors of up to 20, belittling their contribution to the wall. Both ferulates and diferulates enter lignification reactions and become intimately bound up with the lignin complex. Again, under-quantitation is significant since it is not possible to release ferulate or diferulates from some of the structures. Overall, ferulates play a significant role in cell wall development and impact polysaccharide utilization in grasses.