Unraveling the correlation between microbiota succession and metabolite changes in traditional Shanxi aged vinegar

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.

Dynamic microbial succession of Shanxi aged vinegar and its correlation with flavor metabolites during different stages of acetic acid fermentation

“…AAF is responsible for the flavor metabolite formation and organic acid production attributed to microbial succession, in which the bacteria played key roles 9 , 10 . The structure and composition of the microbial community of SAV had been investigated previously in daqu , jiulao and cupei samples using cultural-dependent and cultural-independent methods 12 , 16 , 19 , 25 , 26 . However, it was difficult to explore the AAF using traditional pure cultural technique due to the complexity of the bacterial community.…”

“…For instance, only four bacterial genera including Acetobacter, Lactobacillus, Escherichia and Klebsiella were detected in the AAF using the DGGE method 27 . With the rapid development of sequencing techniques, it is easier to comprehensively characterize the bacterial community of SAV 16 , 17 , 19 , 20 . In this study, more than 15 genera of bacteria (relative abundance > 1%) were identified in vinegar Pei during the AAF fermentation using high-throughput sequencing that was more diverse than those detected by DGGE.…”

“…Similar results have also been reported by Nie et al ., who found that Acetobacter and Lactobacillus are the major bacterial genera in SAV during the AAF process. In addition, the results showed that the microbiota and nonvolatile flavor metabolites produced during AF and AAF were strongly correlated 16 . However, the relationship between the volatile metabolites and various bacteria, and which bacteria boosted the accumulation of the major flavor substance during the AAF process, is still unclear.…”

“…The characteristic aromatic components formed during AAF include organic acids, volatile compounds and amino acids 13 , 14 . It has been reported that 19 volatile compounds and 87 kinds of nonvolatile metabolites that are considered to be aroma-active compounds have been identified in SAV by using GC-MS 15 , 16 . Numerous studies suggest that the diverse volatile or nonvolatile compounds in SAV resulted from the bacterial activity during this period 8 , 10 .…”

Effect of the environment microbiota on the flavour of light-flavour Baijiu during spontaneous fermentation

“…Over thousands of years, humans have optimized the conditions including temperature, moisture, and salinity to promote the growth of certain microbial communities and obtain various fermented foods such as cheese, alcoholic beverages, sourdough, soy sauce, and vinegar 1 , 2 . Although most modern fermented foods are inoculated with defined starter cultures, indigenous microorganisms in traditional spontaneous fermentation are often considered to increase the flavour complexity of these foods 3 .…”