泸型酒酒醅与窖泥中梭菌群落结构、演替和功能差异

Differences of the structure, succession and function of Clostridial communities between jiupei and pit mud during Luzhou-flavour baijiu fermentation

摘要:

梭菌对泸型酒风味品质的发酵形成具有重要作用，但目前对酒醅和窖泥中梭菌群落的物种组成、发酵演替规律以及代谢功能的差异尚缺少深入认识。采用分子微生态学技术，在种水平上对比了同一窖池的酒醅和窖泥中梭菌纲细菌群落的结构差异和演替规律，并通过纯培养方法分离和评价了梭菌菌株的主要挥发性脂肪酸组成差异。结果表明，窖泥发酵过程中梭菌纲细菌和总细菌的基因拷贝数比值相对稳定 (71.5%–91.2%)，而酒醅中梭菌的变化则较大 (0.9%–36.5%)。酒醅中优势梭菌纲细菌主要是梭菌属 (Clostridium，19.9%)、沉积物菌属 (Sedimentibacter，8.8%)和氢孢菌属 (Hydrogenispora，7.2%)，而窖泥中主要为氢孢菌属 (57.2%)、沉积物菌属 (5.4%) 和产己酸菌属 (Caproiciproducens，4.9%)。窖泥及酒醅发酵过程中梭菌群落结构差异显著 (P=0.001)。分离获得的20株梭菌菌株具有不同的产挥发性脂肪酸能力。结果表明，窖池中梭菌纲细菌群落存在时空异质性，其结构和功能差异对泸型酒风味形成具有影响。

Abstract:

Clostridia inhabiting in jiupei and pit mud plays key roles in the formation of flavour during the fermentation process of Luzhou-flavour baijiu. However, the differences of Clostridial communities between jiupei and pit mud remains unclear. Here, the species assembly, succession, and metabolic capacity of Clostridial communities between jiupei and pit mud were analysed by high-throughput sequencing and pure culture approaches. The ratio of Clostridial biomass to bacterial biomass in the pit mud was relatively stable (71.5%–91.2%) throughout the fermentation process. However, it varied widely in jiupei (0.9%–36.5%). The dominant Clostridial bacteria in jiupei were Clostridium (19.9%), Sedimentibacter (8.8%), and Hydrogenispora (7.2%), while Hydrogenispora (57.2%), Sedimentibacter (5.4%), and Caproiciproducens (4.9%) dominated in the Clostridial communities in pit mud. The structures of Clostridial community in pit mud and jiupei were significantly different (P=0.001) throughout fermentation. Isolated Clostridial strains showed different metabolic capacities of volatile fatty acids in pure culture. Spatial and temporal heterogeneity of Clostridial communities existed in the baijiu fermentation pit, which was closely related to the main flavour components of Luzhou-flavour baijiu.