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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Research » Publications at this Location » Publication #213514
Title: WHY COMT-DEFICIENT PLANTS HAVE POOR PULPING PERFORMANCE

Author
item LU, FACHUANG - UNIV OF WISCONSIN
item Ralph, John

Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/1/2007
Publication Date: 6/10/2007
Citation: Lu, F., Ralph, J. Why COMT-deficient plants have poor pulping performance. In: Proceedings of 10th International Congress on Biotechnology in the Pulp and Paper Industry, June 10-14, 2007, Madison, Wisconsin. p. 51.

Interpretive Summary:

Technical Abstract: Transgenic plants that have reduced lignin content, or structurally or compositionally modified lignins, have been studied in order to identify traits with excellent pulping performance. COMT is an enzyme in the monolignol pathway crucial to the synthesis of sinapyl alcohol, one of the two major monolignols in angiosperms. COMT-deficient plants were created and used in pulping trials. The pulping experimental results revealed that COMT-deficient plants have worse pulping performance than the wild type analogs. This was attributed to a lower syringyl:guaiacyl ratio, but that assessment has been found to miss the key reason. Structural analysis of lignins from those COMT-deficient plants showed that a novel monolignol, 5-hydroxyconiferyl alcohol, is incorporated into lignin polymers in COMT-deficient plants, resulting in a unique benzodioxane structures. In this work, lignin dimeric model compounds simulating benzodioxane structures of COMT-deficient lignins were synthesized and subjected to pulping conditions to investigate the effects of benzodioxane structures on pulping efficiency. Our results from pulping experiments using those models as substrates demonstrated that etherified benzodioxane lignin models totally survived alkaline (Kraft or soda) pulping conditions, although phenolic benzodioxane models degraded under the same conditions. Replacement of syringyl units in the polymer, which are largely involved in cleavable beta-ether units, with (5-hydroxyguaiacyl) benzodioxane units which do not cleave, is likely the prime reason why COMT-deficient plants pulp inefficiently.