Efficient Lignin Dissolution and Enzymatic Depolymerization in Ethylene Glycol-Based Deep Eutectic Solvent Mixtures:...

Area of Science:

• Biomass Conversion
• Green Chemistry
• Enzymatic Catalysis

Background:

• Lignin is a key source for aromatic chemicals but its low solubility hinders enzymatic depolymerization.
• Cosolvents are typically needed to increase lignin solubility for efficient processing.

Purpose of the Study:

• To investigate ethylene glycol/choline chloride (EG:ChCl)-based deep eutectic solvents (DES) combined with glycine buffer for lignin dissolution.
• To optimize solvent systems for high-concentration lignin depolymerization using β-etherase.

Main Methods:

• Utilized mixtures of EG:ChCl DES and glycine buffer for lignin dissolution.
• Performed β-etherase-catalyzed depolymerization with high lignin concentrations.
• Employed molecular dynamics (MD) simulations to analyze solvent-lignin interactions.

Main Results:

• Achieved high lignin concentrations (up to 30 g L^-1) without inhibiting enzyme activity.
• Identified optimal conditions (20 g L^-1 lignin, 50% v/v EG:ChCl 4:1) for maximum yield of guaiacylhydroxypropanone and syringylhydroxypropanone.
• MD analyses revealed the roles of EG and glycine in lignin solubility and DES ratio in solvation dynamics.

Conclusions:

• EG:ChCl DES and glycine buffer systems are effective for lignin dissolution and enzymatic depolymerization.
• Solvent composition significantly influences both lignin solubility and the yield of depolymerization products.
• Understanding molecular interactions is crucial for optimizing lignin valorization strategies.