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United States Department of Agriculture

Agricultural Research Service

Title: Ferulate Cross-Linking Limits Degradation of Lignified Grass Walls by Fungal Hydrolases

Authors
item Grabber, John
item Hatfield, Ronald
item Ralph, John

Submitted to: Biotechnology for Fuels and Chemicals Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 1995
Publication Date: N/A

Technical Abstract: Ferulate cross-linking of arabinoxylans to lignin may limit degradation of grass walls by fungal hydrolases. Wall-bound peroxidase and in situ generated H202 was used to form dehydrogenation polymers of coniferyl alcohol within nonlignified walls isolated from maize (Zea mays L.) suspension cultures. Cell walls with 17 and 4.5 mg g**-1 of ferulates were synthetically lignified to Klason lignin concentrations of up to 150 mg g**-1. Ferulate concentrations in cell walls were reduced by growing cultures with 2-aminoindan-2-phosphonic acid or by selectively methylating wall ferulates with diazomethane prior to lignification. Structural polysaccharides in nonlignified walls were extensively degraded (>90%) after a 72 h incubation with hydrolases from Trichoderma reesei and Aspergillus niger. In cell walls with high ferulate concentrations, each unit of lignin reduced structural polysaccharide degradation by 2 units. When ferulate cross-linking of arabinoxylans to lignin was reduced by 70%, structural polysaccharide degradation was increased by 20%. Ferulate cross linking reduced the release of all neutral and acidic sugars from cell walls, particularly that of xylose. Our results indicate that modification of grasses to achieve low ferulate concentrations will improve the enzymatic degradation of structural polysaccharides for bioconversion into ethanol.

Last Modified: 11/26/2014
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