Decoding the temperature and humidity-driven succession of microbial co-occurrence network and its impact on filler tobacco characteristics during agricultural fermentation

Agricultural fermentation is critical in molding the specific quality of filler tobacco leaves (FTLs), which is usually carried out under ambient temperature and humidity changes. Despite this, limited knowledge exists regarding the dynamic interactions between temperature, humidity, microbial communities associated with FTLs, and the specific mechanisms through which these factors influence filler tobacco characteristics (FTC). In this study, free amino acid detection, targeted liquid chromatography-mass spectrometry (LC-MS), and high-throughput sequencing (HTS) were employed to assess the impact of agricultural fermentation on both FTC and microbial communities. Analytical methods, including neutral community models, co-occurrence networks, random forest (RF), partial least squares structural equation modeling (PLS-SEM), and so on, were utilized to investigate the relationships among FTC, fermentation parameters, and microbial dynamics during fermentation. The findings reveal that with extended fermentation time, fluctuations in temperature and humidity intensified environmental survival pressures on the microorganisms, resulting in a decline in microbial diversity. The co-occurrence network declined the number of nodes (123, 102, 96) and edges (580, 395, 376), with increased microbial modularity. Temperature emerged as the primary driver of microbial diversity and composition shifts. Additionally, natural humidity during fermentation had a significant direct impact on FTC ( p < 0.05). Notably, FTC was more strongly influenced by dominant microbial groups than by rare taxa. Overall, the findings underscore that the fermentation process, mediated by temperature and humidity, facilitates the formation of specific microbial groups and symbiotic networks, exerting both direct and indirect effects on FTC. This study emphasizes the critical role of temperature and humidity in agricultural fermentation, offering both practical and theoretical insights for optimizing tobacco fermentation. • Fermentation altered microbial communities and filler tobacco characteristics. • Deterministic and stochastic processes act together in fermentation processes. • Microbial co-occurrence networks were more modular in the late-fermentation stage. • Temperature drove changes in microbial diversity and composition during ferment. • Humidity in the indoor environment affects the characteristics of filler tobacco.