Enhancing Biomethane Production from Corn Stover: Insights into Lignocellulosic Component Interactions and Pretreatment Efficacy

In this study, the methane yield, substance conversion rate and microbial community structure of individual components of lignocellulose, synthetic mixtures, and corn straw subjected to different pretreatments (thermal hydrolysis, chemical, biological, and combined pretreatment) during anaerobic digestion were comparatively investigated. The synthetic mixture of cellulose and hemicellulose (MCXY) exerted a positive promoting effect on biomethane production, with a synergistic effect index of 101. 51%. The methane yield per volatile solids (VS) of microcrystalline cellulose (MC), xylan (XY), and MCXY reached 320. 81 ± 1. 85 mL/g VS, 352. 70 ± 6. 58 mL/g VS, and 340. 60 ± 10. 94 mL/g VS, respectively. Lignin did not produce biogas in anaerobic digestion (AD) system, and its presence had an inhibitory effect on the methanogenesis of cellulose and hemicellulose, especially that of hemicellulose. Notably, pretreatment significantly improved the methane production potential of corn stover. Deep eutectic solvent-pretreated corn stover (DESCS) achieved the highest methane yield of 356. 57 ± 8. 50 mL/g VS, which was 55. 46% higher than that of the untreated group. DES pretreatment deconstructed lignocellulosic matrix and distinctly increased DOM molecular diversity, thus providing superior substrate conditions for improving anaerobic digestion performance. Microbial community analysis revealed that DES pretreatment significantly reshaped the bacterial structure, enriching syntrophic taxa over the carbohydrate-degrading Bacteroides found in raw corn stover, thereby fostering a more robust metabolic network for methane production. While acetoclastic Methanothrix dominated the pretreated groups, its synergistic coexistence with hydrogenotrophic Methanobacterium across all digesters facilitated stable dual-pathway methanogenesis. This work can provide a theoretical basis and technical reference for the optimization and application of pretreatment strategies for efficient anaerobic digestion of corn stover.