Airborne microbes in five important regions of Chinese traditional distilled liquor (Baijiu) brewing: Regional and seasonal variations

Baijiu is one of the six primary distilled spirits in the world. It is produced through the solid-state fermentation of grains in theopen environment, so high-quality Baijiu brewing largely depends on terrior. Environmental microbes are one of the mostimportant factors affecting the quality, quantity, and flavors of Baijiu. As atmosphere is a pool and transport pathway formicrobes from the ambient environment to Baijiu brewing ecosystems, we explored the functional microbes of Baijiu brewing infive important regions. The regions fell into two topographical types, namely, plain and river-valley. In total, 38 functionalmicrobes were identified rich in at least one of the regions, such as the fungi of Aspergillus, Candida, Cladosporium,Debaryomyces, Penicillium, Pichia, Rhizopus, Saccharomyces, and Wickerhamomyces) and the bacteria of Acetobacter, Bacillus,Clostridium, Enterobacter, Lactobacillus, Methanosarcina, Methanobacterium, Methanobrevibacter, and Pseudomonas. However,some functional bacteria (e.g., Clostridia, Gluconacetobacter, and Weissella) and fungi (e.g., Dekkera, Eurotium, Issatchenkia,Mucor, and Phoma) were not rich (relative abundance <0.1%) or were not detected in the atmosphere. Airborne microbiomes andthe Phylogenetic Diversity (PD) index were significantly different between the main brewing season (winter) and the summerbreak in each region, except for the fungi in one region. In winter, airborne microbiomes were significantly different amongalmost all the regions. The relative abundance of bacterial fermentation function in each region increased from summer to winter.The relative abundances of fungal yeast function were higher in winter for the plain regions but were higher in summer for theriver-valley regions. In sum, our results suggested that: (1) atmosphere was one but not the sole important source of functionalmicrobes for Baijiu brewing and (2) microbiomes in different regions might be quite different but they could share some majorfunctions related to Baijiu brewing.