| Vegetable fermentation is a dynamic process of microbial community structure.Different fermentation technologies or fermentation stages have different micro-ecological community structure,so that the fermented vegetables have special flavors and nutrition.Firstly,the bacterial and fungus community structures of 9 fermented vegetables at sale were investigated using PCR-DGGE(polymerase chain reaction-denaturing gradient gel electrophoresis).The fingerprint was proceeded to provide the information for the shannon index,principal component analysis(PCA),and sequence analysis of dominant strips.The results revealed that processing technology had a significant effect on the community diversity and structure of fermented vegetables.For the ones with the same processing technology,the difference of shannon-wiener index was not obvious,and PCA analysis showed that they belong together.Bacterial community structure analysis showed that Lactobacillus groups were rich in all fermented vegetables with different processing technology,packaging process,and raw materials.Lactobacillus plantarum was found in all of the samples.Lactobacillus brevis was predominant in pickled cabbage and sauerkraut.Lactobacillus curvatus was predominant in kimchi and mustard of Zhejiang province.Lactobacillus alimentarius and Lactobacillus fructivorans were the dominant bacteria of sauerkraut and pickles,respectively.Moreover,Psychrobacter sp.was contained in the bulk of mustard and pickles.Enterobacter aerogenes was contained in sauerkraut from two different regions.Besides,No.9 Sauerkraut contained Morganella morganii.No.4 Mustard contained Virgibacillius halophilus.The above bacterium were harmful or conditional pathogenic.In summary,except for the 3 kinds of pickled cabbage,harmful bacteria or conditional pathogenic were found in mustard,pickles and sauerkraut.Fungal community structure analysis showed that yeast was rich in all 9 fermented vegetables at sale.They were respectively Trichosporon mucoides,Zyqosaccharomyces sp.,Basidiomycete yeast sp.,Candida palmioleophlia,Saccharomyces turicensis,and Dabaryomyces sp.The same with the dominant bacteria,Trichosporon mucoides and Zyqosaccharomyces sp.existed in all fermented vegetable samples.Candida palmioleophlia existed in pickled cabbage,mustard,pickled.However,it barely existed in sauerkraut.Dabaryomyces sp.was specific fungal flora of the No.5 mustard.Secondly,combing PCR-DGGE fingerprinting technology with detection of acidity in soup and vegetables in fermented pickles,we explored how the new and old soup impact on the dynamic changes of microbial community structure of the fermentation process,as well as the influence from root vegetables(white radish),stem vegetables(celery),leafy vegetables(cabbage).The results showed that:in fermentation process of the new cabbage soup,there were more significant changes of bacterial community structure in cabbage soup than in celery and radish soup.But they had basically the same fermentation cycle:pre-fermentation in the first 1d,mid-fermentation in the first 2-5d and post-fermentation in the first 6-8d.During pre-fermentation,bacterial diversity and acidity of vegetable and soup was lowest;during mid-fermentation,bacterial diversity and acidity of vegetable and soup increased;during post-fermentation,microbial flora reached a new equilibrium.In addition,in fermentation cycle of new soup,microecological has been formed,so there was no significant effect on fermentation broth when we continued to add vegetables.Bacterial diversity and acidity of vegetable and soup are tended to be stable.Different types of pickled vegetables had a certain influence to microbial diversity,community structure and acidity of pickle soup.The above results have a certain guiding role for production and preservation for traditional fermented vegetables. |
