Application of denaturing gradient gel electrophoresis to microbial diversity analysis in Chinese Douchi.

Background: Douchi is a traditional Chinese soybean food which has been consumed for thousands years as an important protein source and flavouring ingredient. Studies have rarely been carried out to investigate its microbial composition and these are urgently required for the commercial labels and safety considerations.

Results: Microbial counts were statistically significant different among Douchi samples. Although the maximum diversity indexes of bacterial, bacillus and fungal polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) patterns were only 79%, 70% and 64%, some microorganisms, e.g. Bacillus subtilis, Bacillus amyloliquefaciens, Pseudomonas sp., Saccharomyces cerevisiae and Pichia farinose, were found to share dominant positions in most Douchi samples. In addition, some pathogens, e.g. Staphylococcus saprophyticus, Pantoea sp., Staphylococcus sciuri, Enterobacter sp. and Staphylococcus sp., were also identified.

Conclusion: The PCR-DGGE technique was used for the first time as an effective method to assess the microbial communities in different Chinese Douchi samples. This information may be useful in improving the product quality, reformatting production methods, extending shelf life and scaling up the fermentation process.