Plant Biomass Depolymerization by Oxidoreductases: Structural Characteristics, Synergy Mechanism, and Evolutionary Adaptation

Plant biomass, predominantly composed of lignocellulose, exhibits structural and chemical complexity that limits its biological deconstruction. This review evaluates the oxidative strategies utilized by microorganisms, primarily filamentous fungi, to overcome the recalcitrance. We integrate recent experimental breakthroughs with structural bioinformatics to map the expanding landscape of redox enzymes, including newly discovered AA families. Central enzymatic systems involved in lignin depolymerization include laccases and lignin-active peroxidases, whereas polysaccharide-degrading oxidoreductases comprise lytic polysaccharide monooxygenases (LPMOs) and their auxiliary redox partners. Hydrogen peroxide acts as a central intermediate that bridges enzymatic sources with sinks, subject to spatiotemporal regulation. The review also incorporates the synergistic interplay between oxidoreductases and nonenzymatic radical systems, offering refined mechanistic insights. These understandings underpin the design of next-generation biorefineries, accelerating the transition toward a sustainable circular bioeconomy.