Comparison of the microbial communities in pits with different sealing methods for Chinese strong-flavor liquor production

Chinese liquor fermentation is a typical solid-state fermentation process driven by various natural microflora, which is susceptible to ambient influence. A new-type sealing method using stainless steel as the pit cover was adopted as an alternative solution to mitigate the influence. In this study, we investigated the microbial consortia and the flavor metabolites in both the new-type sealing pit (NSP) and the traditional sealing pit (TSP). The study found the concentrations of most flavor metabolites (39 out of 58) in NSP were higher than TSP, and most of them concentrated at the bottom of both pits. The comparison revealed the diversities of microbes in different layers of pits were different (p < 0.05). The compositions of microbiota in different pits were different, albeit Lactobacillus was the absolute dominant genus in both pits. There were 13 dominant genera in NSP and seven in TSP. Therefore, more correlations between microbes were found in NSP, in which the microbial community was more stable. The interplay between different microbes and metabolites consequently resulted in different association patterns in different pits. These findings elaborate on the reasons behind the preference of the new-type sealing method and are instrumental to the optimization of the fermentation process.