A Putative Lignin Copper Oxidase from Trichoderma reesei

Area of Science:

• Biotechnology
• Mycology
• Biochemistry

Background:

• Trichoderma reesei is a fungus utilized for industrial enzyme production.
• Lignin, a complex biopolymer, presents challenges for biodegradation and valorization.
• Understanding fungal interactions with lignin is crucial for biorefining applications.

Purpose of the Study:

• To investigate the ability of Trichoderma reesei to grow on and modify technical soda lignin.
• To identify and characterize key enzymes involved in lignin degradation and modification by T. reesei.
• To explore the potential of T. reesei secretome for lignin valorization.

Main Methods:

• Cultivation of T. reesei on lignin-containing media.
• Quantification of fungal growth and sporulation.
• Analysis of soluble and insoluble lignin fractions.
• Proteomic analysis of secreted enzymes.
• Heterologous production and characterization of a novel copper oxidase (TrLOx).
• Enzymatic assays on lignin-derived molecules and dimers.
• High-performance size-exclusion chromatography (HPSEC) and liquid chromatography-mass spectrometry (LC-MS).

Main Results:

• T. reesei demonstrated growth and sporulation on lignin as a sole carbon source.
• Enzymatic modification of lignin involved oxidative conversion of side chains and cleavage of β-O-4 linkages.
• Polymerization reactions of lignin were observed.
• Five auxiliary activity (AA) enzymes, including a unique copper radical oxidase (TrLOx), were identified in the secretome.
• TrLOx exhibited high stability at alkaline pH, oxidized alcohols and aldehydes, and acted on lignin-derived phenolic molecules and carbohydrates.
• TrLOx displayed polymerizing activity on lignin dimers, forming polymers up to 10 units.
• Synergistic action of TrLOx with other secreted oxidoreductases is suggested for lignin breakdown.

Conclusions:

• Trichoderma reesei possesses the capability to utilize and modify technical soda lignin.
• A novel lignin copper oxidase (TrLOx) from T. reesei plays a significant role in lignin modification and polymerization.
• The identified enzymes and their synergistic interactions offer potential for lignin valorization and biorefining strategies.