Changes and Driving Mechanism of Microbial Community Structure during Paocai Fermentation

Abstract

Fermentation of paocai is a dynamic process of the microbial community structure, and the interaction between community structure and physicochemical factors endows paocai with unique taste and flavor. The study of bacterial and fungal community structure changes and the driving mechanism of physicochemical factors induced changes in community structure, showing that Pseudomonas belonging to Proteobacteria and Lactobacillus belonging to Firmicutes were the dominant bacteria in the process of paocai fermentation. The correlation analysis of physicochemical factors with bacterial community showed that titratable acid was significantly positively correlated with Lactobacillus and negatively correlated with Pseudomonas, while nitrite was the opposite. Redundancy analysis (RDA) showed that pH was positively correlated with the bacterial community in the early fermentation stage, amino acid nitrogen was positively correlated with the bacterial community in the middle fermentation stage, and titratable acid was positively correlated with the bacterial community in the late fermentation stage. Variance partitioning analysis (VPA) showed that environmental factors, pH and metabolites, were the main driving forces of bacterial community diversity, which jointly explained 32.02% of the bacterial community structure variation. To study the glucolysis and nitrogen metabolism in the process of paocai fermentation, we found that in the early stage of the fermentation, the nitrite reductase enzyme of Pseudomonas activity was high, with high nitrite content in the prophase, but by the end of fermentation, lactic acid bacteria rapidly increased, the content of L−lactic acid through the glycolysis pathway, making paocai fermentation environment become acidic, then Pseudomonas decreased. Ascomycota and Basidiomycota were the main phylum fungi in the fermentation process. RDA analysis showed that the fungal community was positively correlated with pH, nitrite, and soluble protein at the early fermentation stage, amino acid nitrogen was positively correlated with the fungal community at the middle fermentation stage, titratable acid and reducing sugar were positively correlated with the fungal community at the late fermentation stage. VPA analysis showed that metabolites were the main driving force of fungal community diversity and accounted for 45.58% of fungal community diversity. These results had a certain guiding significance for the production and preservation of naturally fermented paocai.

Temperature, Salinity and Garlic Additive Shape the Microbial Community during Traditional Beetroot Fermentation Process

“…Shaping the organic acid profile can be associated with the differences in beetroot leaven metabiome composition, and thus, with the diversity in metabolic potential among tested variants. The importance of the metabiome’s composition for determination of organoleptic properties in fermented products has been confirmed in previous studies [ 24 , 25 , 26 ]. It can be concluded that the red beet leaven microbiome is highly sensitive to physicochemical factors.…”

The correlation between flavor formation and microbial community dynamics during the fermentation of zha cai

“…9 Amino acid nitrogen is an important indicator of zha cai flavor. 17 The concentrations of amino acid nitrogen increased significantly at T2 (P < 0.05) and remained stable after T2. The concentrations of salt-free dry matter increased significantly at T2 and decreased significantly at T3 (P < 0.05).…”

“…The increase in total titratable acidity at T2 may be attributed to the accumulation of acid caused by the rapid proliferation of dominant bacteria 9 . Amino acid nitrogen is an important indicator of zha cai flavor 17 . The concentrations of amino acid nitrogen increased significantly at T2 ( P < 0.05 ) and remained stable after T2.…”

“…At present, ensuring the quality and safety of zha cai, increasing the scientific basis for and the rationality of the fermentation process, and controlling the fermentation process are important topics in current vegetable fermentation-related research. 17 Our study tracked the microbial communities of zha cai across fermentation periods. In terms of bacterial composition, Lactobacillus was the dominant bacterium throughout the fermentation process, rapidly converting most amino acids into volatile substances and affecting the flavor of zha cai.…”

“…The differences in microbial community structure result in variations in metabolites produced by microorganisms during the fermentation process of zha cai . At present, ensuring the quality and safety of zha cai , increasing the scientific basis for and the rationality of the fermentation process, and controlling the fermentation process are important topics in current vegetable fermentation‐related research 17 . Our study tracked the microbial communities of zha cai across fermentation periods.…”