PCR-DGGE技术研究淡豆豉炮制过程中微生物菌群的动态变化

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

目的采用PCR-变性梯度凝胶电泳(denaturing gradient gel electrophoresis,DGGE)技术研究淡豆豉Sojae Semen Praeparatum炮制过程中微生物菌群的动态变化,为揭示其炮制机制奠定基础。方法运用PCR-DGGE技术研究淡豆豉炮制不同时间的样本中细菌、真菌菌群种类和数量的动态变化,通过非加权组平均法(unweighted pair-group method with arithmetic means,UPGMA)聚类分析各炮制时间点的菌系差异。结果发酵至"黄衣上遍"过程中细菌种类丰富,真菌以曲霉菌为主;再闷过程中细菌以乳杆菌为主,真菌以隐球菌为主。发酵第1天恶臭假单胞菌、枯草芽孢杆菌占优势;发酵第3天嗜麦芽寡养单胞菌、鞘氨醇杆菌属和米曲霉为优势菌种;发酵第6天解淀粉芽孢杆菌、曲霉菌和丝孢酵母为优势菌种;再闷第3天以枯草芽孢杆菌、丝孢酵母和黑曲霉占优势;再闷第9天以枯草芽孢杆菌、那须乳杆菌、弧形乳杆菌和隐球菌为优势菌株;再闷第15天以枯草芽孢杆菌、弧形乳杆菌、隐球菌、丝孢酵母属和2株不可培养真菌为优势菌。整个炮制过程中,产酸克雷伯氏菌、枯草芽孢杆菌、弧形乳杆菌作为优势菌种始终参与。"黄衣上遍"阶段与再闷阶段的微生物群落结构差异大。发酵第3天与第6天的细菌、真菌群落结构相似度最高,分别达76.4%和66.1%;而发酵第3、6天与再闷第9天的细菌群落结构相似度均最低,仅为24.5%,发酵第3天与再闷第15天真菌群落结构相似度最低,仅11.2%。结论炮制过程中微生物群落结构的动态变化和独特的微生物种类可能决定了淡豆豉特有的性味、功能,同时也从微生物学角度印证了再闷的重要性。

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 Stenotrophomonasmaltophilia, Sphingobacterium sp, and A. oryzae on day 3. Then on day 6, B. amyloliquefaciens, Aspergillus, and Trichosporon ovoidesbecame 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.