Contrasting summer versus winter dynamic microbial communities and their environmental driving factors in the solid-state saccharification process of Fuyu-flavor Baijiu

Abstract

The seasonal spontaneous fermentation depends on the assembly of specific microbiota. However, a knowledge gap remains regarding the seasonal dynamics of microbial community and functionality. This study aimed to investigate the differences in microbial community dynamics during the saccharification process of Fuyu-flavor Baijiu in winter versus summer by employing high-throughput sequencing. It also explored the driving effects of environmental variables on the microbial succession. The environmental temperature of saccharification in summer (29 ± 1 °C) was strikingly different in winter (14 ± 1 °C), leading to a longer incubation time in winter fermentation. The dominant bacterial genera displayed in the early stage of the summer saccharification process were Staphylococcus, unclassified Enterobacteriaceae, and Weissella, whereas the dominant genus was Weissella during the middle stage and Lactobacillus during the late stage of saccharification. In contrast, unclassified Enterobacteriaceae and Weissella were dominant genera throughout the winter saccharification process. In the fungal community, Rhizopus was the dominant genus in summer and winter saccharification. Principal coordinate analysis revealed that the changes in the environmental temperature in winter versus summer had distinct impacts on the microbial community structure. Also, temperature was the key factor driving the succession of bacterial community, whereas pH was the main factor driving the succession of dominant fungi. Predictive gene functionality of bacterial and fungal communities was computed using the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States 2 against Kyoto Encyclopedia of Genes and Genomes (KEGG) database and MetaCyc database, respectively. Correlation networks were constructed to better understand the relationships between dominant microbial genera and physicochemical factors during the saccharification process. These results provided new insights into the Baijiu fermentation technology and allowed a theoretical basis for exploring effective management strategies regarding traditional fermentation in response to complex seasonal factors.

Keywords: Environmental factors; Fuyu-flavor Baijiu; Microbial community; Saccharification; Seasonal variation.