Method for modifying lignin structure using monolignol ferulate conjugates
Inventors
Ralph, John • Grabber, John H. • Hatfield, Ronald D. • Lu, Fachuang
Assignees
US Department of Agriculture USDA • Wisconsin Alumni Research Foundation
Publication Number
US-8569465-B2
Publication Date
2013-10-29
Expiration Date
2030-07-06
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Abstract
Described is an isolated lignified plant cell wall including lignin, wherein the lignin includes a ferulate residue incorporated therein, such as from coniferyl ferulate and/or sinapyl ferulate. Also described is a method to make the isolated lignified plant cell wall, and the lignin produced by the method.
Core Innovation
The invention concerns an isolated lignified plant cell wall including lignin with a ferulate residue incorporated therein, where the ferulate residue originates from monolignol-ferulate conjugates such as coniferyl ferulate and sinapyl ferulate. The method to produce this modified lignin involves conducting a lignin-producing polymerization reaction in the presence of these polymerizable conjugates, resulting in lignin with incorporated ferulate residues. The cell wall may be derived from any plant source capable of lignin production, including genetically modified plants.
Lignin is a highly complex polymer that confers rigidity and aids water transport in vascular plants. It is primarily formed from three monomers: p-coumaryl, coniferyl, and sinapyl alcohols, along with structurally related monomers. The complexity of lignin limits the digestibility of forage in ruminants and obstructs enzymatic saccharification for biofuel or biochemical production. Because lignin is indigestible and inhibits enzyme access to polysaccharides, there is a longstanding need to alter lignins to improve digestibility and fermentability of cell wall polysaccharides.
The invention addresses this need by exploiting the metabolic malleability of lignification, wherein combinatorial radical coupling allows structurally compatible phenolic compounds to be incorporated into lignin. The present method introduces novel monomer conjugates that incorporate ferulate residues into lignin without adversely affecting plant growth. Incorporation up to 60% of these novel monomer residues is achievable, resulting in modified lignin polymers that significantly ease biomass processing for animal feed, paper pulp, biofuels, and chemicals.
Claims Coverage
The claims include three main inventive features related to the isolated lignified plant cell wall, the method of manufacturing modified lignin, and the modified lignin produced by the method.
Incorporation of ferulate-monolignol ester conjugates into lignin
An isolated lignified plant cell wall includes lignin with a ferulate residue incorporated as a ferulate-monolignol ester conjugate, where the monolignol moiety is esterified to the ferulate moiety via a γ-carbon, and both moieties are independently incorporated within the lignin.
Method of manufacturing modified lignin with ferulate-monolignol conjugates
Conducting a lignin-producing polymerization reaction in a cell wall in the presence of at least one polymerizable monomer comprising a ferulate-monolignol ester conjugate, resulting in incorporation of both monolignol and ferulate moieties into the lignin. Preferred monomers include coniferyl ferulate and sinapyl ferulate, with reaction proportions from about 10% to 60% by weight. The polymerization can be in vitro or in vivo, including lignifying isolated cell walls from plant cell suspensions derived from various plants such as maize or specific trees.
Modified lignin produced by polymerization with ferulate-monolignol ester conjugates
A lignin polymer produced by a lignin-producing polymerization reaction in a cell wall in the presence of ferulate-monolignol ester conjugates, specifically where both the monolignol and ferulate moieties are independently incorporated within the resulting lignin polymer.
The claims cover the structural incorporation of ferulate-monolignol ester conjugates into lignin within plant cell walls, the methods to produce such modified lignins through polymerization reactions in cell walls using these conjugates, and the resulting modified lignin polymers, focusing on coniferyl ferulate and sinapyl ferulate as representative monomers.
Stated Advantages
Incorporation of ferulate residues via monolignol ferulate conjugates substantially eases processing of lignified cell walls, facilitating more efficient delignification and enzymatic hydrolysis.
The modified lignins allow biomass polysaccharides to be more efficiently and sustainably utilized, reducing the energy and chemical inputs needed for biomass processing, including pulping and biofuel production.
Plants incorporating up to 60% novel monomer residues show no adverse growth or developmental phenotypes, maintaining structural and functional integrity.
The method enables lignin modification that reduces cross-linking and increases lignin extractability, permitting milder processing conditions and potentially lowering costs and greenhouse gas emissions associated with biomass processing.
Documented Applications
Use of modified lignins for improving forage digestibility and fermentability in ruminant nutrition.
Enhanced pulping processes for papermaking by facilitating lignin extraction under milder alkaline conditions, thus reducing energy and chemical consumption.
Pre-treatment of biomass to improve enzymatic saccharification efficiency for biofuel production, including ethanol fermentation.
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