Metagenomic analysis of microbial community succession during the pickling process of Zhacai (preserved mustard tuber) and its correlation with Zhacai biochemical indices

BACKGROUND: Industrial Fuling Zhacai is pickled by a method summarized as 'three times pickled and pressed', in which raw mustard tubers are subjected to three stages of pickling in different salt concentrations, with a pressing operation at the end of each stage to remove brine. This study used Illumina MiSeq technology and multivariate statistical analyses to investigate microbial community succession during the pickling process and its correlation with Zhacai biochemical indices. RESULTS: A total of 19 phyla, 208 genera, and 295 species of bacteria were identified. Lactobacillus was the dominant genus of bacteria in all three stages and Lactobacillus sakei was the dominant species in the first and second stages. A total of six phyla, 200 genera and 301 species of fungi were also identified. According to a PICRUSt2 prediction, the main functions of the bacterial and fungal communities were carbohydrate and protein metabolism, while alcohol metabolism was also a function of fungi. Nine bacterial genera closely correlated with Zhacai biochemical indices: Acinetobacter, Pseudomonas, Pedobacter, Erwinia, Lactobacillus, Chryseobacterium, Flavobacterium, Duganella, and Paenarthrobacter. Six genera of fungi correlated closely: Penicillium, Cystobasidium, Cladosporium, Plenodomus, Aspergillus, and Simplicillium. All these genera probably originated from the surface microorganisms of raw mustard tuber. CONCLUSION: This study reveals the succession patterns of microbial community structures during the pickling process of industrial Zhacai and infers the core functional flora, providing reference data for Zhacai pickling process control. © 2020 Society of Chemical Industry.