Many microorganisms in the environment participate in the fermentation process of Chinese liquor. However, it is unknown to what extent the environmental microbiota influences fermentation. In this study, high-throughput sequencing combined with multiphasic metabolite target analysis was applied to study the microbial succession and metabolism changes during Chinese liquor fermentation from two environments (old and new workshops). SourceTracker was applied to evaluate the contribution of environmental microbiota to fermentation. Results showed that Daqu contributed 9.10 to 27.39% of bacterial communities and 61.06 to 80.00% of fungal communities to fermentation, whereas environments (outdoor ground, indoor ground, tools, and other unknown environments) contributed 62.61 to 90.90% of bacterial communities and 20.00 to 38.94% of fungal communities to fermentation. In the old workshop, six bacterial genera (Lactobacillus[11.73% average relative abundance],Bacillus[20.78%],Pseudomonas[6.13%],Kroppenstedtia[10.99%],Weissella[16.64%], andPantoea[3.40%]) and five fungal genera (Pichia[55.10%],Candida[1.47%],Aspergillus[10.66%],Saccharomycopsis[22.11%], andWickerhamomyces[3.35%]) were abundant at the beginning of fermentation. However, in the new workshop, the change of environmental microbiota decreased the abundances ofBacillus(5.74%),Weissella(6.64%),Pichia(33.91%),Aspergillus(7.08%), andWickerhamomyces(0.12%), and increased the abundances ofPseudomonas(17.04%),Kroppenstedtia(13.31%),Pantoea(11.41%),Acinetobacter(3.02%),Candida(16.47%), andKazachstania(1.31%). Meanwhile, in the new workshop, the changes of microbial community resulted in the increase of acetic acid, lactic acid, malic acid, and ethyl acetate, and the decrease of ethyl lactate during fermentation. This study showed that the environmental microbiota was an important source of fermentation microbiota and could drive both microbial succession and metabolic profiles during liquor fermentation.IMPORTANCETraditional solid-state fermentation of foods and beverages is mainly carried out by complex microbial communities from raw materials, starters, and the processing environments. However, it is still unclear how the environmental microbiota influences the quality of fermented foods and beverages, especially for Chinese liquors. In this study, we utilized high-throughput sequencing, microbial source tracking, and multiphasic metabolite target analysis to analyze the origins of microbiota and the metabolic profiles during liquor fermentation. This study contributes to a deeper understanding of the role of environmental microbiota during fermentation.

The application of starter is a common practice to accelerate and steer pomegranate wine fermentation process. However, the use of starter needs to better understand the effect of the interaction between starter and native microorganisms during alcoholic fermentation. In this study, high-throughput sequencing combined with metabolite analysis were applied to analyze the effect of commercial Saccharomyces cerevisiae inoculation on the native fungal community interaction and metabolism during pomegranate wine fermentation. Results showed there were diverse native fungi in pomegranate juice, including Hanseniaspora uvarum, H. valbyensis, S. cerevisiae, Pichia terricola and Candida diversa. Based on ecological network analysis, we found S. cerevisiae inoculation transformed the negative correlations into positive correlations among the native fungal communities, and decreased the Granger causalities between native yeasts and volatile organic compounds. This might lead to the decreased contents of isobutanol, isoamylol, octanoic acid, decanoic acid, ethyl laurate, ethyl acetate, ethyl hexadecanoate, phenethyl acetate and 2-phenylethanol during fermentation. This study combined correlation and causality analysis to gain a more integrated understanding of microbial interaction and the fermentation process. It provided a new strategy to predict certain behaviors between inoculated and selected microorganisms and those coming directly from the fruit. IMPORTANCE Microbial interactions play an important role in flavor metabolism during traditional foods and beverages fermentation. However, we understand little about how selected starters influence the interactions among native microorganisms. In this study, we found S. cerevisiae inoculation changed the interactions and the metabolisms of the native fungal communities during pomegranate wine fermentation. This study suggest that the starters inoculation should take into account not only the positive features of starters, but also to characterize the microbial interactions established among the starters and native communities. It may be helpful to select the appropriate starter cultures for winemakers to design different styles of wine.

Uncoordinated carbon-nitrogen ratio in raw materials will lead to excessive contents of higher alcohols in alcoholic beverages. The effect of GAT1 gene, the GATA transcription activator, on higher alcohol biosynthesis was investigated to clarify the mechanism of Saccharomyces cerevisiae regulating higher alcohol metabolism under high concentrations of free amino nitrogen (FAN). The availability of FAN by strain SDT1K with a GAT1 double-copy deletion was 28.31% lower than that of parent strain S17, and the yield of higher alcohols was 33.91% lower. The transcript levels of the downstream target genes of GAT1 and higher alcohol production in the double-copy deletion mutant suggested that a part of the effect of GAT1 deletion on higher alcohol production was the downregulation of GAP1, ARO9, and ARO10. This study shows that GATA factors can effectively regulate the metabolism of higher alcohols in S. cerevisiae and provides valuable insights into higher alcohol biosynthesis, showing great significance for the wheat beer industry.