Fungal diversity during raw vinegar brewing process as revealed by high-throughput sequencing

Abstract:

[Objective] To understand the structure and dynamics of fungal community during raw vinegar brewing. [Methods] In total 51 samples including raw materials, starter, fermenting samples in urns, smoking cupei and leaching cupei were collected from a raw vinegar making enterprise in Shanxi Province, and fungal diversity was analyzed by high throughput sequencing of ITS1 regions. [Results] Except 5 samples having failure amplifications, 489 fungal OTUs were detected in the remaining 46 samples, dominated by Ascomycetes (88.3%). There were significant fungal community differences among groups. The species richness was the lowest in raw materials and starter, the highest in fermenting samples, and medium in smoking and leaching cupei. The dominant fungi from raw materials and starter were Saccharomyces cerevisiae and Aspergillus niger, respectively, which were important inocula for fermentation. There were also obvious fungal community variations during fermentation in urns, which were further divided into early (F2 to F13) and late (F17 to F46) fermentation stages. The abundance of S. cerevisiae and Aspergillus candidus was significantly higher in the early fermentation stage, whereas that of A. niger and Davidiellaceae sp. was significantly higher in the late fermentation stage. [Conclusion] There are significant fungal community variations among different brewing steps and among different fermentation stages in urns. S. cerevisiae and A. niger represent the main fungi contributing to raw vinegar fermentation. This study provides a theoretical basis for the optimization of raw vinegar brewing process.