## 4 Conclusions  
This study revealed the shifts in microbial communities, metabolic transformations, and flavor characteristics during the spontaneous fermentation of Jerusalem artichoke juice. The dominant microbial groups transitioned from environmental bacteria, such as _Flavobacterium_ and _Splingomonas_, to beneficial families like _Lactobacillusae_ and _Acetobacter_acee_ during fermentation, with notable post-fermentation increases in _Actinobacteria_ and _Bacteroidetes_. Secondary metabolites involved in phenylalanine and tryptophan pathways were enriched and lipid and nucleotide metabolic activities were heightened, indicating increased metabolic activity. The increase in phenylpropanol and aromatic amino acid metabolites emphasizes their role in enhancing the flavor and potential health benefits of fermented Jerusalem artichoke juice. Flavor analysis showed significant increases in alcohols, esters, acids, and ketones, contributing to the unique aroma and health benefits of fermented Jerusalem artichoke juice.  
The main advantage of spontaneous fermentation is its ability to preserve the natural flavor and nutritional components of the raw materials without the need for exogenous strains while producing a rich variety of secondary metabolites. The changes in microbial populations are closely linked to metabolic activities during fermentation, with _Lactobacallaceae_ and _Acetobacteraceae_ playing pivotal roles in the later stages, significantly influencing the flavor and quality of the juice.  
However, spontaneous fermentation is sensitive to environmental factors, leading to challenges in controlling microbial community composition and metabolic pathways, which can result in inconsistencies in product quality. Implementing controlled fermentation with selected starter cultures may help mitigate these issues. Future studies should focus on identifying and utilizing beneficial microbial strains to enhance product consistency and safety. These findings provide a foundation for optimizing fermentation processes by controlling environmental conditions and potentially introducing selected starter cultures to enhance the quality and consistency of fermented Jerusalem artichoke products.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/plants13192782/s1](https://www.mdpi.com/article/10.3390/plants13192782/s1)]([https://www.mdpi.com/article/10.3390/plants13192782/s1](https://www.mdpi.com/article/10.3390/plants13192782/s1)), Table S1. Differential Metabolite Screening Results.  
Conceptualization, T.Z.; methodology, T.Z; software, Z.L.; validation, Z.L. and T.Z.; formal analysis, X.L.; investigation, C.C. and X.L.; resources, C.C.; data curation, T.Z.; writing--original draft preparation, T.Z.; writing--review and editing, Y.M.; visualization, C.C.; supervision, Y.M.; project administration, Y.M.; funding acquisition, T.Z. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the Gansu Academy of Agricultural Sciences Scientific Research Conditions Construction and Achievement Transformation Project (2022 GAASS0) and the Science & Technology Project of Gansu Agricultural and Rural Affairs Department (GNKJ-2020-4).  
Data are contained within the article or Supplementary Material.  
The authors declare no conflicts of interest.