传统豆酱发酵过程中细菌多样性动态

细菌在豆酱发酵过程中起到非常重要的作用,并与豆酱的风味和质量密切相关,因此研究豆酱中细菌的多样性具有重要意义。以自然发酵的豆酱样品为研究对象,采用细菌16S rDNA的部分可变区的PCR-DGGE技术对自然发酵豆酱样品的细菌群落组成和优势菌群进行研究。结果表明,传统豆酱发酵过程细菌群体中既有原始种群的减少和增长,也有次级种群的增多和演变。在整个发酵过程中,初期和末期以不可培养细菌为主,初期细菌群体快速演替,细菌种群多样性指数在发酵42 d和56 d达到两次高峰。

The dynamics of bacteria community diversity during the fermentation process of traditional soybean paste

Soybean paste, soy sauce, preserved bean curd and lobster sauce are the four traditional fermentation foods in China. Microorganisms, especially bacterial varieties play an active role during the process of soybean paste fermentation. The bacteria are closely related to the flavor and quality of the soybean paste. In the fermentation of traditional soybean paste, monitoring different stages of the fermentation process and the dynamics of bacteria diversity, as well as controlling the bacteria succession will provide a theoretical basis for strain selection and improvement of the process for industrial production. At present, denaturing gradient gel electrophoresis (DGGE) is widely accepted as a molecular biology tool for studying complex microbial community and behavior. In this study, we used the natural fermented soybean paste as material, extracted bacteria genomic DNA, amplified the V3 region of 16SrRNA genes by PCR, and analyzed the dynamics of bacteria community structure and the dominant population during the fermentation of soybean paste using DGGE. Our results showed that the V3 region of 16SrDNA of the complex microbial community in the fermentation of traditional soybean paste were around 230 bp, containing 19 different gel bands. Sequencing of the DGGE bands revealed the 19 microorganisms, which are Aeromonas, Weissella viridescens, Staphylococcus xylosus, Lactobacillus brevis, Aeromonas media, Staphylococcus saprophyticus, Leuconostoc lactis, Listeria grayi, Bacillus subtilis, Staphylococcus succinu, Bacillus firmus, Tetragenococcus halophilus and six unculturable bacteria. This result clearly reflects the diversity of the bacteria in the fermentation process. Through monitoring the abundance value and degree of dominance during the fermentation process, we found the growth of some initial populations and depression of other initial populations, in addition to the growth and evolution of some subpopulations. The application of PCR-DGGE method in the detection of bacteria diversity has led to valuable information. In addition, the succession of bacteria population displayed the following pattern in the fermentation process based on the Shannon-Weiner index, i.e., the variation of the bacteria population showed "low-high-low" pattern, while the dominant bacteria population showed a succession pattern from D8 (Uncultured Staphylococcus sp.,Accession Number FJ542940.1) to D18 (Uncultured bacterium,Accession Number EU873643.1) and then to D6 (Staphylococcus saprophyticus,Accession Number EU855228.1). At the initial and final stages of the fermentation process, unculturable bacteria population were dominant population, the succession speed was rapid at the initial stage of fermentation. The diversity index of the bacteria population reached peak values at 42 d and 56 d in the fermentation, which were 3.77 and 3.65, respectively. These results have provided important knowledge towards understanding the dynamic changes of bacteria populations in the soybean paste fermentation.