Dehydrogenation Polymer−Cell Wall Complexes as a Model for Lignified Grass Walls

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 KMnO 4 -stained sections revealed that DHPs were distributed throughout the cell wall matrix. DHP−CW complexes were structurally similar to natural grass lignins according to pyrolysis, thioacidolysis, and 13 C-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. Keywords: Gramineae; Zea mays; cell wall; fiber; peroxidase; p -hydroxycinnamyl alcohols; lignin; dehydrogenation polymer; transmission electron microscopy; pyrolysis; thioacidolysis; NMR; fiber degradability