Incorporation of flavan-3-ols and gallic acid derivatives into lignin to improve biomass utilization
Inventors
Grabber, John H. • Ralph, John
Assignees
US Department of Agriculture USDA • Wisconsin Alumni Research Foundation
Publication Number
US-8685672-B2
Publication Date
2014-04-01
Expiration Date
2031-04-19
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Abstract
A method of manufacturing modified lignin and the resulting non-natural modified lignin product in which a lignin-producing polymerization reaction is performed using a polymerizable monomer having the structure:wherein at least one of the polymerizable monomers is incorporated into the resulting lignin.
Core Innovation
The invention discloses a method of manufacturing modified lignin by conducting a lignin-producing polymerization reaction in the presence of one or more polymerizable monomers having specific chemical structures, such as flavan-3-ols and gallic acid derivatives. These polymerizable monomers are incorporated into the resulting lignin to produce a non-natural modified lignin product. The method includes selecting monomers with defined substituents to strategically integrate into the lignin polymer, allowing from about 1 wt % to 100 wt % incorporation, preferably 10% to 60% by weight.
The problem being addressed arises from the complex and heterogeneous nature of natural lignin, which limits digestibility in ruminants, impedes saccharification of structural polysaccharides for biofuel and chemical production, and complicates cellulose pulp production. Natural lignin's resistance to digestion and interference with carbohydrate utilization results in a long-felt and unmet need to alter lignins in a way that improves the digestibility and fermentability of cell wall polysaccharides and reduces production costs and environmental impact of biomass conversion.
The invention leverages the metabolic malleability of lignification, allowing substitution of novel monomers into lignin polymers during biosynthesis without adverse effects on plant growth. By incorporating phenolic compounds such as flavan-3-ols and gallic acid derivatives that can compatibly participate in radical coupling reactions, the modified lignin polymer eases cell wall saccharification and fermentability prior to and following mild chemical pretreatments. This approach offers a significant advance over perturbing monolignol pathways alone, enabling improved biomass utilization.
Claims Coverage
The independent claim sets forth a method of manufacturing modified lignin by polymerizing lignin in the presence of specific polymerizable monomers, with various dependent claims elaborating on the monomer types, ratios, and polymerization conditions. The inventive features focus on monomer selection, compatibility, and the resulting modified lignin products.
Method of modified lignin production via polymerization with specific polymerizable monomers
Conducting a lignin-producing polymerization reaction incorporating one or more polymerizable monomers selected from defined structural groups comprising flavan-3-ols, gallic acid derivatives, and related compounds characterized by specific patterns of substitutions (e.g., hydroxy, alkyloxy, alkanoyl) on aromatic and aliphatic positions.
Polymerization using polymerizable monomers with specific substitution patterns
Carrying out the polymerization reaction with monomers where chemical substituents such as R1 and R2 are independently selected (excluding simultaneous hydrogen), including preferred monomers where R2 is hydrogen and R1 contains defined hydroxy-substituted groups enhancing incorporation into lignin.
Inclusion of catechin and gallate esters as polymerizable monomers
Using specific monomers including catechin, epicatechin, gallocatechin, epigallocatechin, gallocatechin gallate, epigallocatechin gallate, and optical isomers, as well as gallate esters with variable hydroxy substitutions enabling polymerization with lignin.
Controlling polymerizable monomer proportions and reaction context
Reacting from about 10% by weight to about 60% by weight of the polymerizable monomers during polymerization, conducted in vitro or in vivo, optionally in the presence or absence of monolignols such as coniferyl alcohol, dihydroconiferyl alcohol, sinapyl alcohol, and p-coumaryl alcohol.
Modified lignin product resulting from polymerization with defined monomers
Production of modified lignin polymers containing incorporated flavan-3-ols and gallic acid derivatives as an isolated product derived from the described polymerization method with the selected monomers.
The claims cover a method of producing modified lignin by incorporating specified flavan-3-ol and gallic acid derivative monomers into lignin through polymerization reactions, defining monomer structures, incorporation levels, polymerization conditions, and resulting modified lignin products.
Stated Advantages
Improved digestibility and fermentability of cell wall polysaccharides by producing modified lignins that ease saccharification.
Enhanced biomass processing efficiency allowing for reduced production costs and environmental impact in biofuel, chemical, and paper industries.
Capability to incorporate up to 60% novel monomers without adverse plant growth or developmental phenotypes.
Modified lignins possess increased alkaline extractability and reduced lignin-polysaccharide cross-linking, facilitating milder and more effective biomass pretreatment.
Documented Applications
Improving ruminant feed utilization by enhancing forage digestibility and fermentability.
Facilitating industrial conversion of fibrous biomass crops into biofuels via improved saccharification and fermentation.
Enhancing chemical and pulp production from cellulose-containing biomass by producing lignins amenable to milder pretreatments.
Generating modified plant cell walls and isolated lignified tissue with improved processing characteristics.
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