There were some significant differences in the microbial community structure between aged and aging pit mud. The differences in the quantity of Clostridium IV might be involved in the distinction that the aged pit mud has a strong aroma while the aging pit mud does not.

Pit mud plays a crucial role in the production of the Luzhou-flavour liquor. Its quality directly determines liquor quality and yield. The aged pit mud produced good quality liquor but aging pit mud did not. The aim of this work was to investigate the prokaryotic diversity of the aged and aging pit mud from a Luzhou-flavour liquor distillery using molecular methods. Two bacteria-specific and two archaea-specific 16S rRNA gene clone libraries were constructed and analysed using amplified ribosomal DNA restriction analysis. A total of 273 clones were studied, which resulted in 28 operational taxonomic units. Bacteroidetes and Firmicutes predominated in both the aged and aging pit mud, but Synergistetes and Actinobacteria were only detected in the aged pit mud. The family Methanosaeta dominated in the aged pit mud, while the Methanosarcina predominated in the aging pit mud. These results were confirmed using two genus-specific quantitative real time PCR assays. This research distinguished microbial community structure in the aged and aging pit mud for the first time, and has laid an initial foundation for identifying good quality pit mud and for maintaining the quality of pit mud.

The bacterial community in the pit mud of a Luzhou‐flavour liquor distillery in different regions was analysed by combined polymerase chain reaction–denaturing gradient gel electrophoresis (PCR‐DGGE) and quantitative PCR (qPCR) in order to distinguish a matured and a degenerated pit mud, judged according to sensory and physicochemical characteristics. The phyla Firmicutes, Cloacimonetes, Actinobacteria, Proteobacteria, Synergistetes and Unclassified Bacteria were detected. Firmicutes predominated in the pit mud. The diversity and homogeneity of the bacterial community in the matured pit mud were superior to those in the degenerated pit mud in the same distillery. There were significant differences in the bacterial community structure between the matured and degenerated pit mud. Moreover, the bacterial community in the degenerated pit mud samples was similar, which indicated that the bacterial community in the degenerated pit mud did not change within the two different regions. However, the bacterial community in matured pit mud samples was different, demonstrating that there were visible differences in the bacterial community between the samples of matured pit mud collected from the Luzhou‐flavour liquor distilleries in the two different regions. Notably, the quantity of Actinobacteria in the matured and the degenerated pit mud was found to be different by quantitative analysis. Potentially, the Actinobacteria could serve as an indicator bacteria to distinguish between matured and degenerated pit muds. Copyright © 2016 The Institute of Brewing & Distilling

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