空间异质性对大曲微生物群落的影响

Effect of Spatial Heterogeneity on the Microbial Community of Daqu,a Fermentation Starter for Chinese Baijiu

以接种独特母曲生产的浓香型大曲为对象,应用高通量测序技术和常规检测方法,探讨空间异质性对大曲主发酵期微生物群落和理化特性的影响,母曲是由经宇宙射线诱变的大曲逐步扩大培养而成。结果表明,不同层次间驱动因子变化的强度不同,但趋势相同。发酵同期下层曲的发酵特性(液化力、糖化力、酯化力)均高于上层和中层曲,且波动较小。大曲微生物群落主要包括Lactobacillus、Weissella、Bacillus等12个优势细菌属和Pichia、Thermoascus、Rhizomucor等7个优势真菌属。主坐标分析与层次聚类分析表明,各时期和各层次间大曲的细菌和真菌群落聚类方式差异显著。普氏分析与Mantel检验结果表明,水分显著影响大曲的细菌群落,酸度显著影响中层和下层曲的细菌群落,湿度显著影响中层和上层曲的真菌群落。冗余分析结果表明,水分和酸度均与Lactobacillus和Pichia呈正相关,但驱动因子对不同层次大曲微生物群落的影响不同,层次间驱动因子差异性改变了大曲群落中种属间的互作关系及共现模式。因此,调控生产过程中的驱动因子是改善大曲群落结构及品质的有效途径。

The effect of spatial heterogeneity on the microbial community and physicochemical properties during the primary fermentation of Daqu were investigated by high-throughput sequencing technology and conventional detection methods.Nongxiangxing baijiu Daqu inoculated with the unique ripe starter obtained by gradually culturing and expanding Daqu treated by cosmic rays was used.The results showed that although the intensity of change in driving factors varied among layer,their trends were the same.The liquefying,saccharifying and esterifying power of Daqu were higher in the bottom layer than in the upper and middle layers at the same fermentation time and the fluctuation was small.The microbial community of Daqu was composed of 12 dominant bacterial genera,including Lactobacillus,Weissella,Bacillus,Kosakonia,Staphylococcu and Thermoactinomyces,and seven dominant fungal genera,such as Pichia,Thermoascus,and Rhizomucor.Principal co-ordinates analysis and hierarchical clustering analysis showed significant differences in the bacterial and fungal community structure among fermentation stages and layers.Procrustes analysis and Mantel test showed that moisture had a significant effect on the bacterial community in Daqu,and acidity had a significant effect on the bacterial community in the middle and bottom layers of Daqu.Moreover,moisture had a significant effect on the fungal community in the upper and middle layers of Daqu.Redundancy analysis showed that moisture and acidity were positively correlated with Lactobacillus and Pichia,while driving factors had different influences on the microbial communities in different layers of Daqu.Therefore,the interaction and co-occurrence patterns of microbial genera in Daqu could change due to the differences in driving factors among different layers of Daqu.These results suggested that regulating driving factors during the Daqu making process is an effective way to improve the microbial community structure and quality of Daqu.