Study on dynamic changing regularity of microflora in fermentation process of Sojae Semen Praeparatum by PCR-DGGE / 中草药

ABSTRACT

Objective: To reveal the dynamic changing regularity of microflora in the fermentation process of Sojae Semen Praeparatum (SSP) and lay the foundation for revealing the mechanism of SSP processing by denaturing gradient gel electrophoresis (DGGE). Methods: The dynamic changes of microflora, both bacteria and fungi in fermentation process were monitored by PCR-denaturing gradient gel electrophoresis. According to the unweighted pair group method using arithmetic average clustering, the samples of SSP in various stages were analyzed. Results: Bacterial flora had diversity, and Aspergillus was the major fungus in the first stage called "yellow cladding". The major bacteria was Lactobacillus, while the major fungus was Cryptococcus at the "secondary fermentation" stage. The major microorganism was Bacillus subtillis and Pseudomonas putida on day 1, and Stenotrophomonas maltophilia, Sphingobacterium sp, and A. oryzae on day 3. Then on day 6, B. amyloliquefaciens, Aspergillus, and Trichosporon ovoides became the primary microorganisms. B. subtillis, T. ovoides, and A. niger were the major microorganism on day 3 of "secondary fermentation". On day 9 of this stage, the major strains were B. subtilis, L. concavus, L. nasuensis, and Cryptococcus randhawi. On day 15 of "secondary fermentation", they were B. subtilis, L. concavus, C. randhawi, Trichosporon, and two fungi cannot be cultured. Klebsiella oxytoca, B. subtilis, and L. concavus were dominant strains in the whole fermentation process. The composition of microflora in "yellow cladding" stage was different to that of the "secondary fermentation". The microbial community on day 3 and 6 was similar to 76.4%. While the lowest similarity between the samples on day 3 and 9, it was similar to 24.5% during samples on day 6 and 9 in "secondary fermentation" stage. The highest similarity of fungal composition was between day 3 and 6 samples, and the lowest one was between day 3 and 15 of "secondary fermentation", which was similar to 11.2% only. Conclusion: The results show that the unique flavor and function of SSP may be determined by the dynamic microbial communities and microbial flora in the fermentation process, and the secondary fermentation is proved to be irreplaceable from the microbiological point of view.