Differences in Bacterial Community Structure between Bottom and Wall Pit Mud for Nongxiangxing Baijiu

This study was performed in order to understand the differences in bacterial communities and physicochemical indicators between bottom and wall pit mud for nongxiangxing baijiu. Five physicochemical indicators of pit mud were analyzed. High-throughput sequencing technology was used to investigate the bacterial communities, and correlation analysis was carried out between bacterial communities and physicochemical indicators. The results showed that the pH and catalase activity in bottom pit mud were significantly higher than those in wall pit mud (P < 0.05), while the opposite was true for ammonium nitrogen content (P < 0.05). The dominant bacterial phyla in pit mud were Firmicutes, Bacteroidetes, and Synergistetes. The dominant genera in bottom pit mud were Hydrogenispora, Caproiciproduces, Aminobacterium, and Proteiniphilum, the relative abundance of Hydrogenispora being significantly higher than that in wall pit mud (P < 0.05). The dominant genera in wall pit mud were Capriocipiroducens, Lactobacillus, Syntrophaceticus, and Aminobacterium, the relative abundance of Capriocipiroducens, Lactobacillus and Syntrophaceticus being significantly higher than that in bottom pit mud (P < 0.05). The physicochemical indicators and bacterial communities in bottom and wall pit mud were different. Among the physicochemical indicators, pH had the greatest impact on the bacterial community in bottom pit mud, and Hydrogenispora was the iconic genus of bacteria in pit bottom mud. The relative abundance of enzymes involved in acid metabolism was higher in pit wall mud. In conclusion, there were spatial differences in the bacterial communities between bottom and wall pit mud, which could have an important impact on the fermentation of baijiu.