(393d) Stabilization with Formaldehyde Facilitates the High-Yield Production of Monomers from Lignin during Integrated Biomass Depolymerization
Practical, high-yield lignin depolymerization methods could greatly increase biorefinery productivity and profitability. However, development of these methods is limited by the presence of inter-unit carbon-carbon bonds within native lignin, and further by the formation of these linkages during lignin extraction. We show that adding formaldehyde during biomass pretreatment produces a soluble lignin fraction that can be converted to guaiacyl and syringyl monomers at near-theoretical yields during subsequent hydrogenolysis (48-78% of native lignin). We achieved the highest yields using a high-syringyl transgenic poplar with low levels of carbon-carbon linked units. These yields were 3-7 times those obtained without formaldehyde, which prevented lignin condensation primarily by forming 1,3-dioxane structures with lignin side-chain hydroxyl groups. By depolymerizing cellulose, hemicelluloses, and lignin separately, overall monomer yields between 76 and 90% were achieved for these three major biomass fractions.