Screening And Application Of Functional Microbes In Douchi

Douchi, a traditional Chinese fermented soybean food, has gained attention becauseof its health-promoting properties. Until now, its fermentation process is usually an opentype fermentation, which is spontaneous, uncontrolled and often with various pathogenscontamination, which results in potential hazards to food safety and the human body.The determination of safe and reliable microorganisms used during fermentationprocesses is of crucial importance to industrial Douchi production. Here,PCR-denaturing gradient gel electrophoresis (DGGE) and automatic amino-acidanalyzer were used to investigate the microbial diversity and free amino acids (FAAs)content of ten Douchi samples. Then correlations between microbial communities andFAAs were analyzed by statistical analysis. Results indicated that filamentous fungi(Aspergillus oryzae, Rhizopus oryzae, Mucor racemosus), yeasts, Bacillus and lacticacid bacteria were the key players in Douchi fermentation, which were also contributorsto the taste and nutritional properties of Douchi products. After that, an experiment onDouchi fermentation by identified strains was carried out, and then the nutritionalcomposition in Douchi was analyzed. The results showed that it is feasible to fermentDouchi using identified strains and these key players play an important role in thefermentation of Douchi. This is the first report to analyze and confirm the keymicroorganisms during Douchi fermentation by statistical analysis. These results cannot only give us important clues to improve product safety but also serve as afoundation for the industrial production of Douchi.