Dynamics and diversity of a microbial community during the fermentation of industrialized Qingcai paocai,a traditional Chinese fermented vegetable food,as assessed by Illumina MiSeq sequencing,DGGE and qPCR assay

Paocai is a traditional Chinese fermented food and typically produced via spontaneous fermentation. We have investigated the microbial community utilized for the fermentation of industrialized Qingcai paocai using the combination of Illumina MiSeq sequencing, PCR-mediated denaturing gradient gel electrophoresis (PCR-DGGE) and quantitative PCR (qPCR) assay. Three main phyla, namely Firmicutes, Proteobacteria and Bacteroidetes, were identified by both MiSeq sequencing and PCR-DGGE. The dominant genera observed in the fermentation were Lactobacillus, Pseudomonas, Vibrio and Halomonas. Most genera affiliated with Proteobacteria or Bacteroidetes were detected more often during the earlier part of the fermentation, while Lactobacillus (affiliated with Firmicutes) was dominant during the later fermentation stages. Fungal community analysis revealed that Debaryomyces, Pichia and Kazachstania were the main fungal genera present in industrialized Qingcai paocai, with Debaryomyces being the most dominant during the fermentation process. The quantities of dominant genera Lactobacillus and Debaryomyces were monitored using qPCR and shown to be 10⁹–10¹² and 10⁶–10¹⁰ copies/mL, respectively. During the later fermentation process of industrialized Qingcai paocai, Lactobacillus and Debaryomyces were present at 10¹¹ and 10⁸ copies/mL, respectively. These results facilitate further understanding of the unique microbial ecosystem during the fermentation of industrialized Qingcai paocai and guide future improvement of the fermentation process.