Analysis Of Microbial Diversity In Traditional Fermented Sour Congee From Inner Mongolian

Sour congee, a very popular traditional fermentation food, is produced by cereal, such as millet, rice. The microbial composition played the important role in its making technology and quality formation. It is necessary to study microbial composition and biodiversity for quality impoverment and industrialized procuction in future.The PCR-DGGE technology was firstly used to analyze the microbial diversity in this study. CTAB-Lysozyme method was used to extract the total DNA of microbes in sour congee samples. The V3 regions of 16S rDNA and the D1 regions of 26S rDNA were amplified respectively with universal primers 357F-GC/518R and NL1-GC/LS2, and the V3 regions of 16S rDNA was amplified by carrying touchdown PCR. DGGE conditions were optimized for allowing a good separation of the DNA fragments in gels. The region of denaturant gradient was respectively 35%-55% and 30%-55% for gel from PCR products with357F-GC/518R and NL1-GC/LS2. The quantity of loading sample was 15μL, and length of time of electrophoresis was 8 hours in gel.The DGGE was carried out to separate PCR amplicons from twenty-eight sour congee samples. The results showed that microbic diversity in every sour congee sample was abundant. The bacterial DGGE Profiles were more complicated than that of the fungus. There were some dominant bands in every sour sample. Similar community structures of the DGGE profiles were analyzed by clustering methods. A dendrograms was constructed according to Dice similarity coefficient and the UPGMA clustering.The result showed that the majority of samples collected from the same region had a high similarity.In this study, one DGGE ladder consisting of amplicons from nine LABs commonly presented in food were prepared. By comparing the migration distance with the ladder, the microbe in sour congee samples contained probably Lactobacillus plantarum, Lactobacillus fermentum, Leuconostoc mesenteroide, Lactobacillus brevis, Lactobacillus helveticus, Lactobacilus curvatus, Lactobacillus delbrueckii, Pediococcus pentosaceus, and Lactococcus lactis subsp. lactis.The predominated bands were excised and sequenced in the DGGE Profiles. The DNA sequences obtained from each bands were compared to sequences in the NCBI, and then species identification with the highest homology by BLAST search. It was showed that lactobacillus and yeasts was the major microbial composition. Moreover, there were some unknown bacteria in the sour congee. The predominated band presented 87.5% in the sour congee was identified to Lactobacillus helveticus with 100% similarity. The second group was Lactobacillus panis with 98% similaty, and Lactobacillus fermentum with 98% similalty, Lactobacillus brevis with 100% similarity, Lactobacillus plantarum with 99% similarity. Moreover, the strain with 98% simility to Lactobacillus rossiae and the strain with 97% simality to Lactobacillus salivarius was also detected, but they only presented in five samples and one sample, respectively. In addition, uncultured strains and two unknown unidentified strains were found in these samples, and occupited 21.4% and 7%, 7.9%, respectiverly.The predominated fungus were Trichosporon asahii with 99% similarity, Saccharomyces cerevisiae with 99% similarity, Geotrichum sp. with 100% and Issatchenkia orientalis with 100% similarity. Issatchenkia orientalis was frequently detected in most samples and others were presented infrequently.