Analysis of the physicochemical indexes and microbial differences in Huangshui from new and old pits in Qionglai production area

In this study, using Illumina high-throughput sequencing, diversity analysis, and principal coordinate analysis (PCoA), the physicochemical properties and microbial community structure of Huangshui from new (one-year-old) and old pits (over 10 years and over 20 years old) in Qionglai production area were compared. The results revealed that the concentrations of acetic acid, propionic acid, lactic acid, and caproic acid in the Huangshui from the old pits were significantly higher than those from the new pit (P<0.05). Additionally, the contents of reducing sugar and starch in the Huangshui from the old pits increased significantly with the age of the pits (P<0.05). As the pit age increased, the richness and diversity of bacterial communities in the Huangshui of both the new and old pits gradually decreased, while the fungal communities initially decreased and then increased. The Huangshui of different pits ages could be distinguished by PCoA. Lactobacillus and Microascus were the dominant genera in the new pit, while Lactobacillus and Thermoascus were the dominant genera in the old pits. Lactobacillus showed a significant positive correlation with the contents of lactic acid, reducing sugar, and starch (P<0.01), suggesting that Lactobacillus might be the key genus influencing the differences in Huangshui across pit ages and in the fermentation system of Baijiu. Moreover, the fungal genera Monascus and Penicillium were positively correlated with lactic acid, caproic acid, reducing sugar, and starch contents. These findings indicated that changes of pit age had an important effect on the formation of microbial community and its metabolites in the Huangshui.