Abstract：
Daqu is used as the fermentation starter of Baijiu and contributes diversified functional microbes for saccharifying grains and converting sugars into ethanol and aroma components in Baijiu products. Daqu is mainly classified into three types, namely low (LTD), medium (MTD) and high (HTD) temperature Daqu, according to the highest temperatures reached in their fermentation processes. In this study, we used the PacBio small-molecule real-time (SMRT) sequencing technology to determine the full-length 16 S rRNA gene sequences from the metagenomes of 296 samples of different types of Daqu collected from ten provinces in China, and revealed the bacterial diversity at the species level in the Daqu samples. We totally identified 310 bacteria species, including 78 highly abundant species (with a relative abundance >0.1% each) which accounted for 91.90% of the reads from all the Daqu samples. We also recognized the differentially enriched bacterial species in different types of Daqu, and in the Daqu samples with the same type but from different provinces. Specifically, Lactobacillales, Enterobacterales and Bacillaceae were significantly enriched in the LTD, MTD and HTD groups, respectively. The potential co-existence and exclusion relationships among the bacteria species involved in all the Daqu samples and in the LTD, MTD and HTD samples from a specific region were also identified. These results provide a better understanding of the bacterial diversity in different types of Daqu at the species level.
摘要：
大曲被用作白酒的发酵剂，为糖化谷物和将糖转化为乙醇和白酒产品中的香气成分提供了多种功能微生物。大曲主要分为三种类型，即低(LTD)，中（MTD）和高（HTD）温度大曲，根据发酵过程中达到的最高温度。在这项研究中,我们使用PacBio小分子实时测序技术（SMRT）从来自中国十个省份的296个不同类型大曲样品的宏基因组中确定全长16SrRNA基因序列，并揭示了大曲样品在物种水平上的细菌多样性。我们总共鉴定了310种细菌，包括78个高度丰富的物种（每个相对丰度>0.1％），占所有大曲样品读数的91.90％。我们还认识到不同类型大曲中的细菌种类差异富集，在大曲样品中具有相同类型但来自不同省份。具体来说,乳酸杆菌,肠杆菌和芽孢杆菌在LTD中显著富集，MTD和HTD组，分别。所有大曲样品和LTD中涉及的细菌种类之间的潜在共存和排除关系，还鉴定了来自特定区域的MTD和HTD样品。这些结果提供了在物种水平上更好地了解不同类型大曲的细菌多样性。
