Abstract: This study analyzed the prokaryotic community structures of bottom (BPM) and wall (WPM) muds from old and young pits used from the production of Chinese strong-flavor Baijiu by Illumina MiSeq sequencing of the variable V4 region of the 16S rRNA gene. The prokaryotic community from young WPM showed the simplest genus composition, mainly including Lactobacillus (85.59%) and Caproiciproducens (5.63%), followed by young BPM, old WPM and old BPM. The prokaryotic composition of old BPM was the most abundant, with the most abundant being Aminobacterium (11.85%), Sedimentibacter (2.08%) and unknown genera (37.6%). Among the four pit muds, old BPM had the highest values of pH (5.69) and NH4+-N (2.54 g/kg) and the lowest values of alcohol, organic acids, and esters, resulted from the complete metabolic chain of the prokaryotic flora in old BPM. The physicochemical properties of the four pit muds could provide a rationale for understanding prokaryotic evolution during the aging process of pit mud. The number of 16S rDNA copies in old pit mud was 1–2 orders of magnitude higher than that in young pit mud, indicating more prokaryotic abundance in old pit mud. Redundancy analysis revealed that the acetic acid (32.9%) and moisture contents (20.6%) were the most significantly correlated with the prokaryotic community of pit mud (P < 0.01), indicating their importance during PM aging.

Key words: Chinese strong-flavor Baijiu; bottom pit mud; wall pit mud; physicochemical properties; prokaryotic microbial communities