Characterization of Microbial Community and Flavor Compounds in Traditional Fermented Douchi Using HTS and...

This study aim is to elucidate the relationship between the microbial community dynamics and the production of volatile flavor compounds during the fermentation process of bacterial-type Douchi. Using high-throughput sequencing (HTS) and headspace solid-phase microextraction, gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to investigate microbial diversity and volatile compound profiles at different fermentation stages. Spearman correlation analysis was employed to identify potential associations between microbial genera and flavor compounds. The results revealed that the dominant bacterial phyla were Pseudomonadota and Firmicutes, with the dominant genera being Bacillus, Enterobacter, and Weissella. The dominant fungal phyla were Ascomycetes and Mucoromycota, whereas the dominant genera were Aspergillus, Trastula, and Pythium. A total of 110 volatile substances (relative to a relative content ≥ 0.03%) were detected during the fermentation process of bacterial-type Douchi. These included 34 hydrocarbons, 17 alcohols, 11 heterocyclic compound, 10 acids, 9 ketones, 9 esters, 6 aldehydes, 6 sulfur compounds, and 8 other compounds. The characteristic flavor compounds identified were ethanolamine, 2,3-butanediol, benzoaldehyde, 3-hydroxy-2-butanone, pterin-6-carboxylic acid, ethyl heptanoate, and diallyl disulfide. Correlation analysis indicated a strong positive association between benzoin aldehyde and pterin-6-carboxylic acid with the genera Thiobacillus and Pythium. Ethyl heptanoate was positively correlated with Enterobacter, Weissella, and Trasmium. Additionally, 3-hydroxy-2-butanone was positively correlated with the genus Staphylococcus. This research provides valuable insights into the microbial and chemical dynamics of bacterial-type Douchi fermentation, offering guidance for optimizing fermentation processes to improve product quality.