A Static Core in a Dynamic Inheritance: Spatial Partitioning and Redundancy Ensure Century-Long Stability of Jiuyao Microbiota

Traditional solid-state fermented foods rely on stable yet adaptive microbial communities; however, their assembly and inheritance mechanisms remain poorly understood. Jiuyao (酒药), a Chinese fermentation starter propagated for 361 generations, achieves century-‑long stability through a combination of two well-recognized ecological principles: a static core microbiome (dominated by Pediococcus pentosaceus , Weissella cibaria , Saccharomycopsis fibuligera , and Saccharomyces cerevisiae ) and spatially structured functional redundancy. Water content is the primary ecological driver, explaining up to 40.7% of the fungal community succession ( P  < 0.01) and mediating the shift from bacterial-driven acidification to fungal-dominated saccharification. Spatial heterogeneity generates a compensation effect: surface communities (enriched in filamentous fungi) hydrolyze macromolecules, whereas core communities (enriched in yeasts and lactic acid bacteria) drive ethanol production and flavor modification. Core species maintain functional redundancy, buffering inter-annual metabolite variations. This study offers a mechanistic framework for optimizing solid-state fermentation and understanding microbial inheritance in traditional fermented foods.