Bacterial community dynamics during the traditional brewing of Wuyi Hong Qu glutinous rice wine as determined by culture-independent methods

Wuyi Hong Qu (black-skin-red-koji) glutinous rice wine, as one of the most typical representatives of Hong Qu glutinous rice wine in Fujian province of China, is brewed under non-sterile and uncontrolled fermentation condition based on empirical knowledge, causing uncontrollability of fermentation process and instability of the final quality. The objective of this study was to investigate the bacterial dynamics during the traditional fermentation of Wuyi Hong Qu glutinous rice wine using PCR-denaturing gradient gel electrophoresis (PCR-DGGE) and 16S ribosomal RNA (rRNA) gene clone libraries analysis.The DGGE profile indicated that the dominant bacterial species in the traditional wine fermentation starters were Pediococcus pentosaceus, Pediococcus acidilactici and Bacillus sp. (including Bacillus aryabhattai or Bacillus megaterium and Bacillus amyloliquefaciens). Bacterial dynamic obtained from the PCR-DGGE revealed the presence of Bacillus sp. and LAB (including Lactobacillus plantarum group, Lactobacillus brevis, P. acidilactici and P. pentosaceus) during the traditional fermentation process, but they varied in different brewing phases. The relative proportions of some bacterial species (such as Bacillus sp., P. acidilactici, L. brevis and P. pentosaceus) detected at early fermentation stage decreased as the fermentation progressed. While L. plantarum group was consistently detected with high light band intensity throughout the fermentation process. 16S rRNA gene clone libraries revealed that the two different molecular biological methods gave similar results, but clone library analysis was more representative of the bacterial community to some extent. For example, Leuconostoc mesenteroides was detected by 16S rRNA gene clone library but not discovered by bacterial DGGE profile throughout the whole fermentation process. Therefore, the combined approach of nested PCR-DGGE and 16S rRNA gene clone libraries would give a more comprehensive profile of the bacterial dynamics than either alone. Finally, species-specific multiplex PCR was also performed to confirm the L. plantarum group. Result showed that only L. plantarum can be detected from the total bacterial DNA extracted from samples of different fermentation phases.This is the first report to reveal the dynamics of bacterial species involved in Wuyi Hong Qu glutinous rice wine brewing process using culture-independent methods. It might be useful to control wine production systems and improve wine quality.