酱香型白酒大曲和糟醅的细菌多样性分析

Analysis of Bacterial Diversity in Daqu and Fermented Grains for Maotai-Flavor Liquor

采用Illumina HiSeq 2500测序系统全面剖析酱香型白酒中的高温制曲和发酵酿酒阶段的细菌群落结构。结果显示:酱香型白酒高温制曲阶段和发酵酿酒阶段大曲和糟醅的细菌菌群在数量及结构分布上均具有多样性特点,菌群种类基本一致。两个阶段的优势菌门均为厚壁菌门Firmicutes、变形菌门Proteobacteria、放线菌门Actinobacteria、拟杆菌门Bacteroidetes 4类。高温制曲和发酵酿酒生态环境之间存在差异,导致微生物优势菌不同。另外,随着发酵时间的推移,酱香型白酒酿造过程中微生物群落呈现一定的变化规律,大曲样本的细菌菌类变化与贮存时间有关,优势菌属有Clostridium sensu stricto 1、Escherichia-Shigella、Lactobacillus、Streptococcus、Actinobacillus、Bifidobacterium、Peptoclostridium、Mycoplasma、Citrobacter等,诸如Escherichia-Shigella、Actinobacillus、Bifidobacterium、Citrobacter等细菌随贮存时间的延长而增加,Clostridium sensu stricto 1、Mycoplasma等表现为先上升后下降,而Lactobacillus、Peptoclostridium等无明显变化,Streptococcus等细菌呈现下降趋势。而糟醅微生物随窖池发酵(起窖)及高温堆积(下窖)的工艺而不断变化,发酵酿酒阶段的优势微生物为Escherichia-Shigella、Lactobacillus、Clostridium sensu stricto 1、Streptococcus、Actinobacillus、Bifidobacterium、Alternaria。相对丰度较高的细菌菌属中Escherichia-Shigella、Lactobacillus在发酵前期菌数先升高,中期从第2轮次开始下降,第3轮次下窖时达到最低,后期逐渐上升。Clostridium sensu stricto 1、Streptococcus菌群丰度变化规律复杂,呈现先下降后上升的趋势。结果表明:高温制曲与发酵酿酒阶段的优势菌菌属基本一致,说明大曲是后续糟醅发酵的微生物来源。另外,细菌的生长耐受性范围较广,随着时间的推移,温度和水分达到相对平衡,细菌群落也逐渐得到了调整,形成单一菌类为主导的环境,更有利于酱香酒的酿造。

The Illumina HiSeq 2500 sequencing system was used to perform a comprehensive analysis of the dynamics of bacterial community structure during the high-temperature Daqu making process and the fermentation process of Maotaiflavor liquor.The experimental results showed that the population and community structure of the microflora were diverse for both processes and the bacterial species compositions were basically the same.The dominant bacterial phyla were Firmicutes,Proteobacteria,Actinobacteria,and Bacteroidetes for both process.The ecological environment was different between the two processes,resulting in variability in the dominant bacterial community composition.In addition,the bacterial community regularly changed during the fermentation process of Maotai-flavor liquor.The change in the bacterial community in Daqu was related to storage time.The predominant genera in Daqu were Clostridium sensu stricto 1,Escherichia-Shigella,Lactobacillus,Streptococcus,Actinobacillus,Bifidobacterium,Peptoclostridium,Mycoplasma and Citrobacter.The abundance of Escherichia-Shigella,Actinobacillus,Bifidobacterium and Citrobacter increased with increasing storage time,the abundance of Clostridium sensu stricto 1 and Mycoplasma first increased and then decreased,the abundance of Lactobacillus and Peptoclostridium did not obviously change,and the abundance of Streptococcus showed downward tendency.The bacterial community in fermented grains changed from pit fermentation to high-temperature stacking fermentation.The dominant microorganisms during the liquor fermentation process were Escherichia-Shigella,Lactobacillus,Clostridium sensu stricto 1,Streptococcus,Actinobacillus,Bifidobacterium and Alternaria.The numbers of Escherichia-Shigella and Lactobacillus,having higher relative abundance,increased during the early fermentation period,then decreased from the second round until reaching a minimum at the high-temperature stacking fermentation stage of the third round,and finally increased gradually again during the late fermentation stage.The abundance of Clostridium sensu stricto 1 and Streptococcus decreased first and then increased.Taken together,our results revealed that the dominant genera during the high-temperature Daqu making process and the liquor fermentation process were basically the same,which indicates that Daqu is the microbial source for the fermentation of fermented grains.In addition,the growth tolerance of bacteria was strong.As time went on,the variations of temperature and water reached an equilibrium,and the bacterial community was gradually dominated by a single species,which is more conducive for the brewing of Maotai-flavor liquor.