Microbacterium testaceum facilitates polysaccharide decomposition during post-harvest aging of tobacco leaves by recruiting keystone bacterial taxa

The use of functional microorganisms is a widely adopted, green, and efficient industrial technique for enhancing tobacco leaf quality. These microorganisms accelerate the degradation of macromolecular organic substances. However, their impact on the chemical composition of tobacco leaves across different aging durations and the mechanisms of polysaccharide degradation remain unclear. This study analyzed the degradation patterns of starch, pectin, cellulose, and hemicellulose at different time points (3 h, 2 months, 6 months, 36 months) during the tobacco aging process after the addition of Microbacterium testaceum, and compared the differences in microbial community structure, diversity, and molecular ecological networks. The results showed that compared with sterile water treatment of the tobacco leaf aging process, the exogenous addition of Microbacterium testaceum accelerated the degradation of polysaccharide macromolecules, and the highest degradation rate of starch was 17.4% at the aging stage of 2-6 months, and the highest degradation rate of pectin was 45.46% at the aging stage of 6-36 months. At the same time, the exogenous addition of Microbacterium testaceum altered the microbial community structure during the tobacco aging process by increasing the number of core functional microorganisms, such as Delftia and Proteus, which promoted microorganisms that play a role in material degradation in the ecological environment of tobacco aging. This study provided a theoretical basis for the regulation of interspecific microbial interactions by exogenous functional strains over a broad timescale (from 3 h to 36 months) during tobacco aging, thereby promoting the degradation of polysaccharide macromolecules.