The Laccase-Lig Multienzymatic Multistep System in Lignin Valorization.

Area of Science:

• Biotechnology
• Biochemistry
• Polymer Science

Background:

• Lignin depolymerization is crucial for valorizing biomass into biofuels and chemicals.
• Existing methods often lack efficiency or specificity in breaking down complex lignin structures.
• Enzymatic approaches offer a promising, environmentally friendly alternative for lignin modification.

Purpose of the Study:

• To design and develop a multienzymatic system for efficient lignin depolymerization.
• To investigate the cleavage of non-phenolic aryl glycerol β-O-4 aryl ether bonds using a laccase-Lig cascade.
• To elucidate the influence of lignin structure on the depolymerization and polymerization reactions.

Main Methods:

• Utilized a sequential enzymatic system combining laccases (Bacillus licheniformis, Funalia trogii) and the Lig system (Sphingobium sp. SYK-6: LigE, LigF, LigG).
• Applied the system to pristine, Kraft, and Organosolv lignins.
• Analyzed structural modifications in residual lignins and quantified low-molecular-weight products.

Main Results:

• The laccase-Lig system successfully cleaved non-phenolic aryl glycerol β-O-4 aryl ether bonds.
• Lignin depolymerization was observed in samples with a low phenolic/aliphatic hydroxyl group ratio.
• Lignin polymerization occurred in samples with an increased phenolic/aliphatic hydroxyl group ratio.

Conclusions:

• The developed laccase-Lig system effectively depolymerizes lignin by targeting specific ether linkages.
• Lignin's inherent structural characteristics, particularly the phenolic/aliphatic hydroxyl ratio, critically determine the outcome (depolymerization vs. polymerization).
• This enzymatic strategy offers tunable control over lignin modification based on its source and structure.