Understanding the Shifts of Microbial Community and Metabolite Profile From Wheat to Mature Daqu

Abstract

Wheat-originated microbes play an important role in shaping the quality of high-temperature Daqu which is commonly used as a starter for producing sauce-flavor Baijiu. However, the shifts of microbiota from raw material to fresh Daqu and then to mature Daqu remain unclear. Hence, in the present study, the inner and outer of fresh and mature Daqu were collected to explore the correlation between microbiota and metabolites as well as the source of the microbiota in Daqu. Results indicated that the activities of amylase and protease between the inner and outer of fresh Daqu varied significantly while both parts became similar after maturation. The predominant bacteria shifted from Saccharopolyspora (outer) and Staphylococcus (inner) to Kroppenstedtia (both outer and inner), while the predominant fungi shifted from Thermoascus (both outer and inner) to Byssochlamys (outer) and Fusarium (inner). A combining analysis of headspace solid-phase micro extraction-gas chromatography-mass spectrometry, headspace gas chromatography-ion mobility spectrometry, and nuclear magnetic resonance was employed to detect the metabolites. The network analysis was conducted to perform the relationships between microbes and metabolites. The results showed that the bacteria, especially Saccharopolyspora, Bacillus, and Acinetobacter, had a strong correlation with the productions of esters, amino acids and their derivatives, and sugars and their derivatives, while most fungi such as Thermoascus, were negatively correlated with the phenylalanine, trimethylamine n-oxide, and isovalerate. SourceTracker analysis indicated that wheat was the important source of the Daqu microbiota, especially, the microorganisms in the inner of Daqu might be the drivers of the microbial succession during maturation. This study provided a comprehensive exploration to understand the microbial sources and shifts in high-temperature Daqu during maturation.

Unraveling the Effects of Biochemical Drivers on the Bacterial Communities and Volatile Profiles in Refrigerated Sturgeon Filets at 4°C

“…However, there is limited research focusing on the biochemical and quality changes of sturgeon filets during refrigerated storage. Although Zhang Y. et al (2021) , Zhang Z. et al (2021) reported on the microbial changes of sturgeon being stored at ice temperature, only the specific spoilage organisms (SSOs) were evaluated. The effects of biochemical drivers on the bacterial communities and volatile profiles of refrigerated sturgeon filets at 4°C are still unknown.…”

The Risk Monitoring of Aflatoxins and Ochratoxin A in Critical Control Point of Soy Sauce Aroma-Type Baijiu Production

“…Daqu is a traditional fermentation starter of soy sauce aroma-type baijiu made of wheat and used throughout the fermentation process of making baijiu [15,30]. Thus, it is the essential material for soy sauce aroma-type baijiu production.…”

Comparative analysis of the microbiotas and physicochemical properties inside and outside medium-temperature Daqu during the fermentation and storage

“…However, the microbial composition and physicochemical indices in Daqu undergo continuous succession during production due to environmental factors ( Fu et al, 2021 ). Meanwhile, different microbiotas and physicochemical properties have been observed in different parts of the same Daqu brick due to the difficulty in transferring heat, water, and oxygen ( Jin et al, 2019 ; Chen et al, 2020 ; Zhang Y. et al, 2021 ). The aforementioned results all affect the quality of Daqu .…”

“…Therefore, analyzing the microbiotas and physicochemical indices inside and outside the Daqu during production might provide a scientific theory for establishing a relatively comprehensive method to evaluate the quality and control the process of Daqu . Some studies on these have been performed ( Jin et al, 2019 ; Chen et al, 2020 ; Zhang Y. et al, 2021 ). Jin et al (2019) revealed that the dominant microbes and volatile flavors on the surface and the core of soy-flavor Daqu had different distribution characteristics and found that microbial interactions were stronger in the core than on the surface ( Jin et al, 2019 ).…”