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Biomass Fundamentals Module 13 : Lignin

Biomass Fundamentals Module 13 : Lignin. A capstone course for BioSUCCEED : Bio products S ustainability: a U niversity C ooperative C enter of E xcellence in ED ucation. The USDA Higher Education Challenge Grants program gratefully acknowledged for support.

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Biomass Fundamentals Module 13 : Lignin

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  1. Biomass FundamentalsModule 13: Lignin A capstone course for BioSUCCEED: BioproductsSustainability: a University Cooperative Center of Excellence in EDucation The USDA Higher Education Challenge Grants program gratefully acknowledged for support

  2. This course would not be possible without support from: USDA Higher Education Challenge (HEC) Grants Program www.csrees.usda.gov/funding/rfas/hep_challenge.html

  3. Lignin • Anselme Payen 1838: Reacts wood with nitric acid and then sodium hydroxide. Remaining material he names Cellulose. • Schulze 1857: Names dissolved material Lignin from the latin lignum meaning wood. • Phenolic Polymer - The Glue that Holds the Fibers Together • 3 Dimensional Crolinked Network • Branched Polymer/Polydisperse (Large and Small Polymers)

  4. Lignin Biosynthesis I

  5. The Metabolic Pathways for the Biosynthesis of Wood Components hν

  6. Shikimic Acid Pathway • The Primary Metabolic Pathway for Lignin • Shikimic Acid Pathway • Occurs in all plants • Leads to Lignin –Tannins and Extractives • The whole pathway is enzymatically controlled

  7. The 6 Carbon sugar is initially spit into 2 units Condensation Cyclization Reduction of Carbonyl to OH Activation Using ATP- Install P at C5 Another PEP is used to extend the chain, P falls off as H3PO4 Aromaticity is finally installed followed by Transamination (NH2)

  8. Lignin Biosynthesis II • The Cinnamate Pathway is a secondary metabolic pathway • Specific to Woody Plants • Creates the Lignin Precursors …the Lignin monomers • Cinnamyl alcohols

  9. Lignin Biosynthesis II CH2 CH2 CH2

  10. Dehydrogenative Polymerization of Lignin precursors • Monolignols are NOT abundant in their free forms • exist as 4-O-b-D-glucosides • Monolignol-glucosides • Increase solubility - Facilitate transport • Decrease toxicity

  11. LigninNomenclature

  12. LigninNomenclature Side Chain } Phenylpropane Unit C9 Common Names

  13. Polymerization-Initiation Enzymatic Formation of Phenoxy Radical Creating a Phenoxy Radical Peroxidases-H2O2 systems cause proton abstraction from a given cinnamyl alcohol

  14. Lignin Polymerization Process • Dehydrogenation - formation of phenoxy radicals • Coupling - formation of oligolignols and quinone methide • Addition of water, lignols, carbohydrates and acids - formation of -hydroxyl group, -O-4 linkages and lignin-carbohydrate complex

  15. Lignin Polymerization • Repetitive dehydrogenation of lignols, coupling and addition to quinone methide • Lignol is a collective name for precursors and intermediate products of lignin during lignification. (Similar to saccharides) • Monolignol - precursors • Dilignol, triligonol, tetralignol, etc. • Oligolignol

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