During fermentation of Jiang-flavor-Baijiu, several complex microbial communities (i.e., bacteria, yeasts, and molds) are readily involved and mainly residue in the raw material (sorghum), heap fermented grains, Daqu, and pit mud (Figure 2) (Yang et al., 2020a,b). In terms of heap fermentation, microbiota become enriched on the surface of the raw materials and produce Baijiu-flavor precursors such as alcohols, carboxylic acids, and esters (Tang et al., 2021). The core communities in the fermented grain liquor starters include lactic acid bacteria and Bacillus (Bacillus amyloliquefaciens, Bacillus licheniformis and Lactobacillus sp.), as well as yeast (Saccharomyces cerevisiae, Candida, Hansenula polymorpha, Hansenula anomala, and Pichia pastoris), Aspergillus (Aspergillus, Monascus, Aspergillus flavus, Monascus purpureus, Aspergillus niger, Aspergillus nidulans, and Aspergillus fumigatus), Thermomyces, Rhizopus, and Mucor (Mucor plentus, Mucor pusillus, Mucor racemosus, and Mucor racemosus) (Fan et al., 2006) (see Figure 3).

High-temperature Daqu is a typical starter for Jiang-flavor-Baijiu as the saccharification and fermentation starter (Wu et al., 2023). The microbial community structure of Daqu is important for developing quality and flavor as the primary microbial and enzyme source (Zuo et al., 2020). The microbiota such as Aspergillus, Thermoactinomyces, Lentibacillus, Bacillus, Kroppenstedtia, Staphylococcus, and Saccharopolyspora in Daqu decompose macromolecular substances in fermented grains, providing aroma substances or precursors of aroma substances that determine the flavor of Baijiu (Wang et al., 2020). Daqu can be categorized as low-temperature Daqu (peak temperature < 50°C), medium-temperature Daqu (peak temperature range in 50–60°C), and high-temperature Daqu (peak temperature > 60°C) (Jin et al., 2020). Given the adaptability of Baijiu fermentation microbiota to temperature, microbial community structure in Baijiu Daqu varies with temperature category. For example, bacteria rather than fungi predominate in Jiang-flavor-Baijiu Daqu, such as Thermoactinomyces, Saccharopolyspora, Streptomyces, Brevibacterium, Staphylococcus, Lentibacillus, Kroppenstedtia and Bacillus (Wang et al., 2020). These microbes are adapted to high temperatures and represent the unique diversity of Jiang-flavor Baijiu.

In the fermented grains, the fungi Ascomycota, Zygomycota, Chytridiomycota, and Basidiomycota are most prevalent; Ascomycota accounts for 94% at the phylum level. At the genus level, Aspergillus, Emericella, Candida, Monascus, Pichia, Wallemia, Trichosporon, and Wickerhamomyces are the primary contributors (Table 1). The predominant fungi in Baijiu fermented grains are Aspergillus (2.70–50.02%) and Monascus (15.08–52.47%). Bacteria and fungi residue in raw material, Daqu, and fermented grains secrete enzymes (glucoamylase, liquefying enzyme, and protease) that decompose starch, protein, and other macromolecular substances into flavor substances (Wang et al., 2008; Wang M. Y. et al., 2018; Yang et al., 2019). Thus, the microbial community structure in Baijiu fermentation is an important determinant of Baijiu quality and flavor. The correlation between Baijiu fermentation microbial community and their quality is subsequently reviewed.

Owing the difference in fermentation raw materials and technical procedure, the microbial community structure and metabolism procedure of Jiang-flavor-Baijiu are varied in comparison with other types of Chinese Baijiu (i.e., Laobaigan-flavored baijiu, Fuyu-flavored baijiu, and Feng-flavored baijiu), which vary in their decomposition of starch, cellulose, and polysaccharides from raw materials (Wang X. et al., 2017; Wang X. D. et al., 2017; Wang Z. et al., 2018). For example, Lactobacillus promotes the Maillard reaction and produces lactic acid-related organic acids and diacetyl via sugar fermentation (Yang et al., 2020b). Pichia anomala, a saccharomycete, generates acetic acid, octanoic acid, lactic acid, phenylethyl alcohol, 2,3-butanediol, ethyl tetradecanoate, and 2-furanethanol (Kong et al., 2014). Saccharomyces cerevisiae produces β-glucosidase during fermentation process and further promotes the release of monoterpenes from glycoside precursors (Zha et al., 2018). Thus, many flavor substances are detected in Baijiu, which contribute to distinctive scent and flavor profiles (Table 2). Jiang-flavor-Baijiu has a complex characteristic scent generated by esters (ethyl acetate, ethyl butyrate, ethyl caproate, ethyl caprylate, and ethyl lactate), alcohols (isobutanol, butanol, isoamyl alcohol, phenylethyl alcohol, and furfuryl alcohol), carboxylic acids (acetic, propionic, butyric, and caproic acids), ketones (3-hydroxy-2-butanone, furfural, benzaldehyde, and phenylacetaldehyde), and phenols (guaiacol and tetra-ethyl guaiacol) (Niu et al., 2017). These substances usually have special aromas, such as fruity short-chain fatty acid esters; floral aromatic compounds; nutty pyrazines; cellar bottom: medium- and short chain fatty acids (Li et al., 2017). Baijiu flavor substances are produced by fermentation microbiota via enzyme degradation and microbial interactions. Understanding the mechanisms of these processes is important to unravel how Baijiu flavor profiles develop.

Enzymatic degradation and production of Baijiu flavor substances are mediated by secreted enzymes, including lipase, amylase (α-amylase, β-amylase, saccharifying amylase and γ-amylase), cellulase, esterification enzymes, pectinase, and tannase. During solid-state fermentation (Li et al., 2019). These enzymes accelerate the conversion of starch, cellulose, protein and fat to smaller molecular weight flavor substances such as glucose, fructose, fatty acids, and esters (Zhu et al., 2022). In sorghum, α-amylase in amylase reacts amylopectin to produce dextrin, maltose, and glucose, and with amylose to produce oligosaccharides, maltose and glucose (Li et al., 2019). Cellulase (produced by Bacillus subtilis, Trichoderma, Aspergillus and Penicillium) hydrolyzes lignin and cellulose; protease hydrolyzes protein into amino acids, the precursor of other Baijiu flavor substances; and the amino acids also provide nutrients to support the growth of microbes in the community. Lipase decomposes fat in raw materials into glycerol, fatty acids, monoglycerides and diglycerides (Li et al., 2019).

In addition to enzymatic degradation, complex microbial interactions also contribute to the formation of flavor substances in Baijiu fermentation (Meng et al., 2015). Mutualism, parasitism, antagonism, predation, and competition among Baijiu-making microbiota inhibit some populations and induce others, influencing the population structure in different Baijiu manufactories and generating different flavor profiles. For instance, populations that include Aspergillus oryzae XJ10 and Saccharomyces cerevisiae produce more esters, aldehydes, ketones, and ethyl acetate than either species alone, indicating that Aspergillus oryzae XJ10 and Saccharomyces cerevisiae produce a synergistic effect and unique fermentation product (Chen et al., 2014). Other microbes, in the Baijiu fermentation system can interfere with the growth of some fermenting populations. For instance, Saccharomyces cerevisiae CCTCCM2014463 inhibits the growth of Zygosaccharomyces bailii CGMCC4745, but has no significant effect on Bacillus licheniformis CGMCC3962 and Lactobacillus buchneri (Xu et al., 2018). Similarly, Saccharomyces cerevisiae is also able to impact the growth of Lactobacillus bread when co-existence with each other, the presence of Saccharomyces cerevisiae in fermentation system is available to produces ethanol and inhibits the growth and reproduction of Lactobacillus bread and lactic acid accumulation (Liu et al., 2022a).

The unique soil types of Jiang-flavor-Baijiu production workshops include red soil (purplish red mudstone, purplish red rock and soil and mixed purplish red clay) and yellowish brown soil (yellowish brown sandstone and clay) (Li et al., 2017). These soils contain abundant minerals and trace elements that support microbial growth and reproduction. A recent study showed that the content of rare-earth elements (REE) (i.e., Samarium (Sm), Europium (Eu), Erbia (Er), and Cerium (Ce)) in the surface soil Jiang-flavor-Baijiu producing area (287.1 μg/g) was than that in soil (186.8 μg/g) and crust (207 μg/g) for other areas of mainland China (Jiang et al., 2023). The rich mineral elements in the soil can improve the quality of Baijiu: by increasing the mineral content of the water, composing sealed mud pits and cultivating high-quality raw materials. Soil minerals support Baijiu fermentation microbiota and improve the quality of water, sealed mud pits, and raw materials, thus indirectly improving Baijiu quality.

The sealed mud pits are considered as the ideal habitat of fermentation microbiota. Under sealed fermentation conditions, different microbiota in the sealed mud pits continue to metabolize and affect Baijiu flavor (Li et al., 2023). During Jiang-flavor-Baijiu fermentation, the purple red mud was extensively utilized as sealed pit mud due to its specific signatures, including low sand content, strong viscosity, and well sealing performance. In addition, the purple red mud is of moderate in acid and alkali, rich in a variety of beneficial components (organic matter content ~1%), and rich in mineral nutrients (SiO₂: 52–74.7% (average 60.1%); Fe₂O₃: 5.28–7.43% (average 6.51%); Al₂O₃: 11.7–17.6% (average 15.6%)) (Liu and Tan, 2011). This will facilitate for Baijiu fermentation microbial growth and community succession, indicating that soil quality is an important determinant of high-quality Jiang-flavor-Baijiu fermentation. A recent study investigated the microbial community structure in fresh red soil, sealed mud pits used for 1 month and sealed mud pits used for 12 months near the producing area of Jiang-flavor-Baijiu, and discovered abundant microbiota residue (Wang et al., 2015a). The abundance of microbial populations was greater in fresh soil used for sealed mud pits (81 families) than in sealed mud pits used for 1 month (77 families) and 12 months (47 families), suggesting the number of microbial species decreased with increasing age of Maotai red soil as sealed mud pits (Wang et al., 2015a). In addition, there are 12 families of microbiota were detected in fresh soil and in sealed mud pits used for 1 and 12 months (Wang et al., 2015a). During the long-term domestication of microbiota in cellars, the content of high-efficiency fermentation microbiota continues to increase, an important determinant of improved Baijiu quality. Hence, in red and yellow soil surrounding the Jiang-flavor-Baijiu manufacturing workshop can be used as sealed mud pits and transfer abundant Baijiu fermentation process, influencing the Baijiu flavor over the long-term.

High-quality red and yellow soil surrounding the Baijiu manufacturing workshop yields high-quality raw materials essential to the Baijiu fermentation microbial community and flavor because these materials support the energy and habitat for microbial growth. The diverse content of amylopectin and amylose in sorghum from different Baijiu-producing areas generates differences in water absorption and gelatinization capacities during the manufacture of Baijiu and koji, affecting saccharification efficiency and other differences in the community structure of Baijiu-making microbiota. In addition, differences in starch content and structure in different types of sorghum will also lead to a variety in the composition and structure of amino acids after enzymatic hydrolysis, thereby affecting the content and composition of flavor substances (alcohols, aldehydes, carboxylic acids and esters) (Ding et al., 2024; Ma et al., 2022). Hongyingzi sorghum used in Jiang-flavor-Baijiu brewing is a unique, organic waxy sorghum characterized by its small grain, thick skin and full grain. The total starch content of Hongyingzi sorghum is >65%, and amylopectin accounted for 88–93% of the total starch content, giving it characteristics of small grain, thick skin, full and solid, and able to withstand nine rounds of cooking. In contrast, the Hongyingzi sorghum in which mainly produced in Renhuai, Guizhou, China (105°–106 °E and 27°–28° N latitude) are planted with mid-subtropical monsoon climate conditions (average annual temperature of 18°C). This further induced the Hongyingzi sorghum became a symbol as the raw material of the unique flavor Jiang-flavor-Baijiu.

The water for Jiang-flavor-Baijiu fermentation comes from the Chishui River Basin, which has an intact natural ecology and exiguous industrial and anthropogenic activity. In addition, the Chishui River contains many trace elements beneficial to human health that are also discovered in red soil, leading to the high-quality Jiang-flavor brew water being moderate in acidity and rich in minerals and trace elements (Li et al., 2017). The basic Chishui River water quality parameters are as follows: pH: 6.5–8.5, total hardness: 2–7 mmol/L, nitrate nitrogen: <0.2 mg/L, free chlorine residual: < 0.1 mg/L, consistent with high-quality brew water requirements (pH: 8.1, total hardness: 6.2 mmol/L, nitrate nitrogen: 0.5 mg/L, free chlorine residual: < 0.3 mg/L) (Li et al., 2017). Previous effort has focused on the microbial community structure in the Chishui River, and discovered substantial fermentation microbiota residue (Jin et al., 2009), thereby unravel the preliminary fermentation microbiota in environmental media is necessary to improve the quality of Baijiu. Jiang-flavor-Baijiu fermentation microorganisms Actinobacteria, Bacteroidetes, Proteobacteria, and Firmicutes have been detected year-round in the Chishui River using 16S rRNA gene sequencing analysis. Proteobacteria was the dominant species, followed by Firmicutes, Actinobacteria, and Bacteroidetes (Tan et al., 2014). The microbial community structure in the Chishui River and water intake sites at Baijiu manufactories also revealed the presence of Baijiu fermentation microbiota, including 55 phyla, 167 classes, 415 orders, 706 families, and 1,431 genera. Pseudomonas (16.99%) and Massilia (12.45%) were the dominant species (Lv et al., 2021).

However, during long-term Baijiu manufacturing activities, the discharge of wastewater will influence nearby water quality despite wastewater treatment efforts, affecting water quality (pH), chemical oxygen demand (COD), and ammonia nitrogen (NH₃-N) and possibly influencing the brewing microbial community structure. Using COD and NH₃-N as example, a recent study discovered that the quality of the water intake at Maotai Distillery is significantly different from that of the upstream/downstream water intake, with COD concentration 7.22 ± 0.01 mg/L in the water body at the intake section of the distillery less than the upstream 8.62 ± 0.07 mg/L and downstream concentrations 8.36 ± 0.05 mg/L. The NH³-N concentration 0.51 ± 0.02 mg/L in the Baijiu water intake is greater than upstream 0.28 ± 0.01 mg/L and downstream concentrations 0.33 ± 0.01 mg/L (Lv et al., 2021). This is due to the fact that continuous Jiang-flavor-Baijiu making activities inevitable discharge varied organic contaminants (fertilizers and natural manure) into the water, accelerating oxygen the consumption and the formation of NH³-N, leading to the COD and NH³-N in the Baijiu making water intake section higher than that of the upstream river. Simultaneously, the COD and NH³-N associated contaminants produced by Baijiu making areas are readily to be degraded and diluted during the surface runoff, resulting the COD and NH³-N concentration Baijiu making water intake section higher than that of the downstream river consequently (Lv et al., 2021). Redundancy analysis showed that the concentration of COD_Mn, COD, and DO in the water of Jiang-flavor-Baijiu fermentation areas also determined the diversity of microbial community structure. Taking DO as an example, unclassified_Comamonadaceae, Sphingorhabdus, Flavobacterium, and Pseudarcicella were significantly positively correlated with DO (p < 0.05), while unclassified_Micrococcaceae and Pedobacter were significantly negatively correlated with DO (p < 0.05), verifying that water quality is an important determinant of the structure and function of bacterial communities in the ecosystem surrounding Baijiu brewing areas (Lv et al., 2021).

There were significant differences in the microbial community structure in the water body of the Baijiu brewing area and upstream/downstream water of the water intake, with Pseudomonas (15.33%) and Acinetobacter (14.99%) being the dominant species. Acinetobacter (22.21%) and Flavobacterium (16.84%) were the dominant microbiota upstream of the water intake, while Pseudomonas and Massili were the dominant microbiota downstream of the water intake (Lv et al., 2021). We conclude that long-term Baijiu-making activities have led to a significant difference in water quality between Baijiu regions and waters upstream and downstream of the manufactory intakes. This difference drives the specific distribution of microbial community structure in Baijiu regions. The intake water is rich in minerals that have an important impact on Baijiu flavor. The content of sodium (21,000 μg/L), magnesium (67,000 μg/L), chlorine (27,000 μg/L), manganese (14.47 μg/L), and iron (164.4 μg/L) in the water of Jiang-flavor Baijiu is much higher than that of Luzhou Laojiao (sodium: 12783 μg/L, magnesium 5,886 μg/L, chlorine 22,776 μg/L, manganese 3.77 μg/L, and iron 37.9 μg/L) and Wenjun Distillery (sodium 8,065 μg/L, magnesium 5,103 μg/L, chlorine 10,773 μg/L, manganese 2.1 μg/L, and iron 23.9 μg/L), indicating that there are abundant mineral elements in the water of Jiang-flavor-Baijiu (Wang et al., 2022a). These inorganic salt ions improve the formation of flavor substances and improve the quality of Baijiu during fermentation.

As with water, microbiota in the air are also an important source of microbiota in Jiang-flavor-Baijiu. A recent study explored the dominant microorganism species in the air around the Jiang-flavor Baijiu brewing area and found a relativity stable microbial community structure that varied with the seasons, such as Acinetobacter, Arthrobacter, Aspergillus, Bacillus, Brevibacterium, Cedecea, Pichia, and Rhodoceccus (Wang et al., 2022a). This variability may be due to the unique geographical location of the Jiang-flavor-Baijiu brewing area, which is surrounding by mountains. The airflow is slow (wind speed 1.3–1.35 m/s), the annual average temperature fluctuates little (the average temperature from 1961 to 2018 was 15.1°C, SD (standard deviation) 0.34°C), and the annual average precipitation fluctuates stably (average precipitation from 1961 to 2018 was 1018.6 mm, SD 10 mm), resulting in a stable microbial community structure in the area and reduced influence of external environment (Wang et al., 2022a). The primary bacteria in the air of Jiang-flavor-Baijiu brewing areas are Streptomyces, Acinetobacter, Staphylococcus, Bacillus, Brevibacterium, Brevibacterium, Kocuria, and Pseudomonas. The dominant fungi are Aspergillus, Cladosporium, and Pteris. Thus, fermentation microbiota residue in the Jiang-flavor Baijiu brewing area originated from surrounding environment, highlighting the critical impact of brewing microbial community structure on the flavor of Jiang-flavor Baijiu. For example, For example, Zhou et al. (2024) discovered that bacterial communities of phyla Actinobacteriota, Firmicutes, and Proteobacteri, as well as fungal communities of Ascomycota and Basidiomycota were predominant airborne microbiomes residue in the Jiang-flavor Baijiu core production areas, whereas the Saccharomonospora, Thermoactinomyces, Bacillus, Oceanobacillus, and Methylobacterium contributing were demonstrated as core functional flora to the Baijiu producing according to the Random Forest analysis (Zhou et al., 2024). Relative Bacillus amounts in the air surrounding the Baijiu-making workshop, koji-making workshop, and outdoor air surrounding the workshop were also assessed in the Daqu, sealed pit mud, and fermented grains (accumulated fermented grains and pit fermented grains), including B. licheniformis, B. amyloliquefaciens, B. subtilis, Paenibacillus lactis, Bacillus lentus, Paenibacillus sp., and Staphylococcus lentus. Fermentation microbiota in the Daqu, pit mud and fermented grains exhibited obvious homology with the microbial community structure of surrounding air, indicating that air exposure is an important contributor to Baijiu-fermentation microbiota.

To bridge the knowledge gap unraveling the role of environmental factors (monsoon climate, temperature, wind speed, humidity, and precipitation) on shaping microbiomes during Jiang-flavor-Baijiu brewing, correlations between environmental factors and microbial community structure indicators (ACE index and Chao index) were thus established (Wang et al., 2022b), which favoring to understood the bacterial diversity and community dynamics during Jiang-flavor-Baijiu open fermentation process. For instance, Beecroft et al. (2012) developed the microbial communities surrounding the Jiang-flavor manufacturing workshops (indoor dust, windows, sills, and wall surfaces) using high throughput sequencing analysis (Beecroft et al., 2012). They discovered 33 bacterial classes (Gammaproteobacteria, Bacilli, Sphingobacteriia, Alphaproteobacteria, Actinobacteria, Flavobacteriia, and Betaproteobacteria), 153 bacterial families (Enterobacteriaceae, Sphingobacteriaceae, Bacillaceae, Flavobacteriaceae, Thermoactinomycetaceae, Planococcaceae), and 396 bacterial genera (Sphingobacterium, Enterobacter, Pantoea, Acinetobacter, Oceanobacillus, and Pseudomonas) (Beecroft et al., 2012). The bacterial community structure was significantly correlated with the surrounding environment (temperature, sunlight, humidity, atmospheric pressure, and precipitation) (Wang et al., 2022b). The unique natural environmental factors and their influence on Baijiu fermentation microbial communities were systematically reviewed.

Temperature is important in microbial dynamics and diversity during fermentation, especially in the Daqu making (Garcia et al., 2023; Simon et al., 2020; Walker et al., 2018; Zhang et al., 2023). Alphaproteobacteria, Acetobaqcteraceae, Sphingomonadaceae, Caulobacteraceae, and Brevundimonas were positively correlated with the fermentation temperature, with p values were 0.350, 0.488, 0.283, 0.290, and 0.284, respectively. In contrast, Bacillaceae (p = 0.489), Bacillus (p = 0.387), Oceanobacillus (p = 0.419), Thermoactinomycetaceae (p = 0.284), and Kroppenstedtia (p = 0.347) exhibited a negative correlation with fermentation temperature (significance defined as p < 0.5) (Beecroft et al., 2012). These results highlighted the important role of temperature in the domestication and screening of microbial community structures during fermentation. Jiang-flavor Baijiu manufacturing facilities are located in the Guizhou province, southwest China, which is a subtropical climate with high temperature and humidity that facilitate microbial growth. The temperature of Jiang-flavor-Baijiu manufacturing workshop is reported as in the range of 2.7°C–40.6°C, with an annual average temperature of 17.4°C, which provides a suitable habitat for the growth and reproduction of fermentation microbiota (Li et al., 2017).

A seasonal subtropical climate brings precipitation (annual precipitation from 1961–2018: 1018.6 ± 10 mm), resulting in a relatively high air humidity to the Jiang-flavor Baijiu making regions, and influencing the Baijiu brew microbial growth and propagation (Li et al., 2017). The abundance of Gammaproteobacteria (p = 0.342), Enterobacteriaceae (p = 0.376), Escherichia-Shigella (p = 0.366), and Pantoea (p = 0.367) were positively correlated with humidity, while Rhodospirillales (p = 0.363), Acetobacteraceae (p = 0.298), and Actinobacteria (p = 0.359) were negatively correlated with humidity (Wang et al., 2022b). Bacillaceae, Lentibacillus, Thermoactinomycetaceae, and Lactobacillaceae were also reported to correlate significantly with precipitation. Thus, humidity and regional precipitation significantly affect Baijiu fermentation microbial diversity. Microbial respiration and growth decrease with decreasing air humidity and temperature (Cruz-Paredes et al., 2021).

Moreover, the geology of Jiang-flavor-Baijiu regions creates unique wind speed and direction conditions that drive seasonal variations in the type and abundance of Baijiu brew microbial species and Baijiu quality (Tan et al., 2014). Microbes in air influence Baijiu manufacturing and a steady wind direction and speed facilitate consistent transfer of microbes from the air to the fermentation raw material, especially during open static fermentation of Jiang-flavor Baijiu. Wang et al. (2022b) characterized the variations of wind speed in a Jiang-flavor manufacturing workshop (Chishui River basin, China) from 1961- to 2018, and discovered that the multi-year wind speed variation is 1.33 m/s, with the wind speed increasing at 0.014 m s⁻¹ every 10 years (Wang et al., 2022a). The Jiang-flavor-Baijiu manufacturing workshop is located in a closed basin area (103°36′–109°35’N, 24°37′–29°13′E) surrounding by mountains, and has low wind velocities. This unique topography favors stability in the Baijiu brew microbial community structure and facilitates stable flavor and quality in the product (Jiang et al., 2009). The Jiang-flavor-Baijiu manufacturing workshops are located in low-latitude mountainous areas and are subject to subtropical monsoons. The climate is warm and humid, with sufficient rainfall to support the growth of fermentation microbiota. In addition, the Jiang-flavor-Baijiu factories are located in a basin that is relatively closed, supporting long-term stability in the wine-making microbial community structure and essential to the high quality of Jiang-flavor-Baijiu. Thereby, from the perspective of environmental microorganisms, we can conclude that long-term Baijiu making activities and regional suitable climatic conditions will lead to a relatively stable microbial community structure in the water, air and soil surrounding the Baijiu producing area, resulting the quality of Baijiu produced by new distilleries is not as good as that produced by old distilleries. This is assigned to the close correlation among the regional geological structure (location, wind, humidity, and water quality), Baijiu brewing microbial community structure, composition of microbial metabolites, and liquor flavor. These also highlighted the fact protecting the ecology of Jiang-flavor-Baijiu plays essential role in maintaining the stability of Baijiu fermentation microbial community and their special flavors.

Environmental factors driving the microbial community structure are also varied within the Baijiu fermentation system. For instance, Yang et al. (2023) developed the changes of microbial community structure succession during 1–6 rounds of Jiang-flavor-Baijiu stacking process and discovered that, with the continuous progress of the stacking process, the dominant bacterial genera are readily to be replaced from Lactobacillus to Acetobacter, while the fungal genus are readily to be replaced from Pichia to Candida (Yang et al., 2023). With the Jiang-flavor-Baijiu fermentation transfer from the stacking heap fermentation to pit fermentation, microorganisms also changed consequently according to the high-throughput sequencing analysis. The abundance of Pichia decreased whereas the abundance of Saccharomyces began to increase and act as one of the dominant fungal species within the fermentation system. Meanwhile, in comparison with stacking heap fermentation, the bacterial species of Lactobacillus and Saccharomyces increased continuously, and Lactobacillus contributing >80% to total bacterial abundance during pit fermentation process (Hao et al., 2021). Environmental driving factors controlling the successive changes of microbial communities during Jiang-flavor-Baijiu brewing are responsible to the multiple constituents of temperature, moisture, sugar content, ethanol, acidity, lactic acid (Yang et al., 2023). Specifically, lactic acid, ethanol, acidity, and temperature were found to positively correlated with Lactobacillus and Saccharomyces; acetic acid was demonstrated to negatively controlled the abundance of Virgibacillus and Bacillus; and water was reported to negatively controlled the abundance of Virgibacillus, Bacillus, Oceanobacillus, taphylococcus, and Kocuria simultaneously (Hao et al., 2021). These highlighted a comprehensive environmental factors for natural meteorological and Baijiu fermentation system on the specific Baijiu brewing microbial succession.