Tianjie Ao

Conventional biorefining of lignocellulosic biomass, such as corn stover (CS), is hampered by poor carbon efficiency, as nearly half of the substrate carbon is lost as CO₂ during ethanol fermentation. This study presents a holistically integrated cascade process designed to capture and valorize all major carbon streams. The system synergistically couples three stages: (1) high-productivity ethanol fermentation (1.68 g/L/h) using the engineered yeast Saccharomyces cerevisiae CE10; (2) anaerobic digestion of the resulting stillage, which efficiently converted residual organics into methane (171 L/kg COD) with ca. 80% COD removal; and (3) cultivation of the cyanobacterium Desertifilum tharense BERC03 using the nutrient-rich digestate and captured fermentation CO₂. This integrated approach boosted the carbon utilization from a baseline of 48% to 62%. A comprehensive techno-economic analysis of an industrial-scale (2000 t/d) facility projected a Minimum Ethanol Selling Price (MESP) of $2.44 per gallon, a value approaching current market competitiveness. The analysis identified the feedstock (30%) and cellulase (17%) as the primary cost drivers. These findings demonstrate a validated biorefinery model that significantly enhances carbon recovery and outlines a viable pathway for the coproduction of multiple biofuels from lignocellulosic resources.

The development of a cost-effective process for biomass conversion into sugar platforms is a cornerstone of sustainable biorefining. Here, we report a Lewis acid-controlled catalytic strategy for nonenzymatic sugar production from hemicellulose in biomass using a highly active, magnetically separable core–shell catalyst. The catalyst comprises a Fe₃O₄ magnetic core, an acid-resistant silica interlayer, and a phosphorus (P)-doped porous carbon shell. Under mild hydrothermal conditions, the optimized catalyst (MC₆₀₀P_1.2) achieved a xylose yield of 86.9% from xylan (100 °C for 2 h) and 60.3–91.0% from diverse biomass feedstocks (corncob, corn stover, poplar, and bamboo, 160 °C for 2 h), outperforming previously reported systems. Such remarkable catalytic activity is attributed to the unique structural design of the catalyst. The silica interlayer acts as a protective shield of Fe₃O₄ core and bonds with the carbon layer to form a silica–carbon shell that provides an ideal scaffold. Meanwhile, P doping introduces defects and hydrogen bonds, enhancing the active site accessibility. The formation of thermally stable PO_x species (C–P–O, C₃–PO, and C–O–P) on the carbon support acts as Lewis acid sites. C–P–O efficiently activates H₂O to produce H⁺ for glycosidic bond cleavage and suppresses xylose degradation, ensuring a high yield. These features result in high catalytic stability and reusability, maintaining high xylose yields after three consecutive cycles. This work provides new research avenues to produce nonenzymatic sugar based on active, deactivation-resistant, and easily recoverable heterogeneous catalysts.