Dye-Decolorizing Peroxidases Maintain High Stability and Turnover on Kraft Lignin and Lignocellulose Substrates

Area of Science:

• Biotechnology
• Enzymology
• Bioremediation

Background:

• Fungal enzymes like laccases and peroxidases are known for lignin degradation.
• Dye-decolorizing peroxidases (DyPs) from fungi and bacteria also modify lignin but are challenging to study.
• Existing methods lack continuous kinetic analysis for DyP activity on complex substrates.

Purpose of the Study:

• To determine kinetic parameters of bacterial and fungal DyPs on insoluble plant materials and kraft lignin.
• To assess the stability and continuous activity of DyPs using real-time hydrogen peroxide monitoring.
• To validate a novel kinetic method for studying DyP enzymes.

Main Methods:

• Kinetic analysis of bacterial DyP (Amycolatopsis 75iv2) and fungal DyP (Auricularia auricula-judae).
• Monitoring hydrogen peroxide (H2O2) depletion using a H2O2 sensor.
• Substrates included insoluble plant materials and kraft lignin.
• Product formation validated using mass spectrometry.

Main Results:

• Both bacterial and fungal DyPs exhibited significant activity on kraft lignin, with fungal DyP being nearly three times more active.
• Real-time H2O2 monitoring revealed exceptional enzyme stability under turnover conditions.
• Bacterial DyP achieved 24,000 H2O2 turnovers, while fungal DyP reached 94,000 turnovers in 1 hour.
• The H2O2 sensor method was validated by mass spectrometry, correlating H2O2 depletion with product formation.

Conclusions:

• Bacterial and fungal DyPs are robust enzymes with significant potential for lignin modification.
• Real-time H2O2 monitoring provides a reliable method for assessing DyP kinetics and stability.
• This study advances the understanding of DyP enzymes in lignocellulose degradation.