ARS | Publication request: DEHYDROGENATION POLYMER-CELL WALL COMPLEXES AS A MODEL FOR LIGNIFIED GRASS WALLS

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 3, 1995
Publication Date: N/A

Interpretive Summary: Fiber makes up 15 to 80% of the dry weight of plants. Fiber is composed primarily of two types of polymers, polysaccharides and lignin. Polysaccharides can be degraded to simple sugars by enzymes. These sugars are an important source of energy for humans and livestock.These sugars may also be converted into ethanol for use in automobile fuels or other purposes. Polysaccharides in fiber are poorly degraded into simple sugars because of their association with lignin. Scientists do not understand how lignin prevents polysaccharides from being degraded by enzymes. Therefore, we have developed a simple system or model to study how lignin prevents polysaccharides from being degraded. In our system, we isolate plant cell fiber that is composed of only polysaccharides. We then form an artificial lignin within this fiber. Using many types of tests, we have found that fiber containing artificial lignin is very much like natural fiber made by plants. We are now using this system to test how different kinds of lignin affect the degradation of polysaccharides by enzymes. We will use the results of this work to develop plants that are used more efficiently as a source food and fuel energy.

Technical Abstract: p-Hydroxycinnamyl alcohols were efficiently polymerized into maize walls by wall-bound peroxidases and in vitro generated hydrogen peroxide to produce dehydrogenation polymer-cell wall (DHP-CW) complexes. Electron microscopy of KMnO4 stained sections revealed that DHPs were distributed throughout the cell wall matrix. DHP-CW complexes were structurally similar to natural lgrass lignins according to thioacidolysis, pyrolysis, and **13C-NMR spectroscopy. Nonlignified walls were rapidly degraded by rumen microorganisms and by commercial fungal hydrolases, whereas DHP-CW complexes had a reduced rate and extent of degradation. This system is useful for modeling matrix interactions in lignified walls and for identifying means of improving the utilization of lignocellulosic materials for nutritional and industrial purposes.