Abstract
Shanxi aged vinegar (SAV) is a well-known vinegar produced by traditional solid-state fermentation and has been used in China for thousands of years. However, how microorganisms and their metabolites change along with fermentation is unclear. Here, 454 high-throughput sequencing and denaturing gradient gel electrophoresis were used to investigate the composition of microbial community. Metabolites were further analyzed by gas chromatography–mass spectrometry and high–performance liquid chromatography. Results showed that the composition of bacterial community changed dramatically at different stages of fermentation. The bacterial genera (relative abundance > 0.1%) decreased from 17 in daqu (starter used in starch saccharification) to 2 at the 12th day of alcohol fernemtation (AF). 15 bacterial genera at the 1st day of acetic acid fermentation (AAF) decreased to 4 genera, involving Acetobacter (50.9%), Lactobacillus (47.9%), Komagataeibacter (formerly Gluconacetobacter, 0.7%) and Propionibacterium (0.1%) at the 7th day of AAF. The structure of fungal community was more homogeneous. Saccharomyces and Saccharomycopsis were predominant in AF and AAF. A total of 87 kinds of nonvolatile metabolites were detected. Canonical correspondence analysis showed a significant correlation between the microbiota succession and the formation of metabolites during the fermentation of SAV. This study provides detailed information for the fermentation mechanism of traditional SAV.
Highlights
Shanxi aged vinegar (SAV), a well-known vinegar used in China for more than 3,000 years, is produced by traditional solid-state fermentation
The V3–V5 regions of 16 S rRNA was amplified for 454 sequencing, and the results indicated that 477,223 raw sequencing reads with an average read length of 441 bp were obtained
A total of 297,126 high-quality sequences with an average read length of approximately 317 bp were obtained after low-quality and chimera sequences were removed (Supplementary Table S1)
Summary
Shanxi aged vinegar (SAV), a well-known vinegar used in China for more than 3,000 years, is produced by traditional solid-state fermentation. Focusing on microbial succession in single or double fermentation processes, the culture-independent techniques involving denaturing gradient gel electrophoresis (DGGE)[4, 5, 8,9,10,11,12] and high-throughput sequencing[3, 13] are applied in the microbiota analyses of vinegars. Several environmental factors, such as oxygen, heat, temperature, acidity, and salinity[14], may influence the structure and biodiversity of a microbial community. We tried to establish 1) how metabolites changed along with the succession of microbial community during the fermentation process of SAV, and 2) the correlation between metabolite changes and the variation of microbial community
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