Microbe-enzyme synergistic fermentation enhances tobacco stem cell wall degradation by modulating enzymatic activity and microbial community structure

The valorization of tobacco stems, a major agricultural by-product with high lignin content, is hindered by the recalcitrance of plant cell walls. Conventional approaches using single microbes or enzymes suffer from inefficiency, instability, and poor performance on lignin-rich substrates. To address this, we proposed a “microbe-enzyme synergistic” strategy by combining Bacillus megaterium (a multifunctional degrader) with its own extracellular enzymes. Three treatments were designed: microbe-only (T b ), enzyme-only (T e ), and microbe-enzyme combination (T b&e ), with sterile water as the control (CK). Cell wall component contents, enzyme activities, and microbial community structure were analyzed after 7 days of fermentation. The T b&e treatment achieved the most substantial degradation: 64.93% for cellulose, 57.89% for lignin, and 37.20% for pectin, significantly outperforming T b and T e . It also exhibited the highest activities of cellulase, laccase, and pectinase. High-throughput sequencing revealed that T b&e specifically enriched Bacillus megaterium (94.97% of the community) while suppressing non-functional competitors. Our findings demonstrate that the synergy creates a positive feedback loop: initial enzymatic hydrolysis facilitates microbial colonization, which in turn boosts sustained enzyme production. This study elucidates a mechanistic model for efficient biodegradation and provides an innovative strategy for the high-value utilization of high-lignin agricultural wastes.