Tandem Mechano-Enzymatic Catalysis: A Green Revolution in Lignocellulosic Biomass Pretreatment via Contact-Electro-Catalysis

The recalcitrance of lignocellulosic biomass poses a critical bottleneck in sustainable biorefining, where conventional pretreatments rely on energy-intensive, chemically hazardous, or thermally extreme processes. Here, we introduce a tandem mechano-enzymatic strategy using contact electrocatalysis (CEC), a newly emerging mechanocatalysis method, to enable green, efficient, and scalable biomass deconstruction followed by enzymatic hydrolysis. By synergizing ultrasound-driven mechanical disruption with recyclable SiO2 microparticle catalysts, the CEC method achieves over 80% degradation of raw wheat straw within 4 h under ambient conditions─without high temperatures, toxic solvents, or irreversible catalysts. Such degradation is enabled by the reaction with free radicals generated by SiO2 microparticle catalysts, which maintain good performance even after five cycles. High-level quantum chemistry calculations were also adopted to explore possible reaction pathways. Compared to the conventional ultrasound pretreatment, the CEC pretreatment significantly enhances cellulose and hemicellulose conversion efficiencies by 35.8% and 78.1%, respectively, while reducing cellulose crystallinity by 12% (CrI = 32.44 vs 36.94 for raw biomass). This structural modification facilitates subsequent enzymatic hydrolysis, yielding glucose concentrations comparable to energy-intensive ball milling. More importantly, the tandem strategy eliminates secondary waste generation and leverages reusable catalysts, aligning with the circular economy. Our work establishes CEC as a transformative pretreatment paradigm, bridging the gap between industrial scalability and sustainable biomass valorization for biofuels and bioproducts.