Studies On The Fermentatfon Mechanism And Healthy Functions Of Bacteria-fermented Douchi

Lobster sauce is a unique flavoring made of black bean or soybean by the microbialfermentation, which possesses abundant functional group such as soluble nitrogen, solublesugar, vitamin A, vitamin B family, vitamin E, soybean oligosaccharides, soybean isoflavone,soybean saponin, brown pigment, soybean polypeptide.Bacterium lobster sauce is a food by the protease from Bacillus Subtilis Natto on cookedsoybean. As a representation of water lobster sauce from bacterium, there is no interrelatedreport as well as the systematic research on its fermentation mechanism and its physiologicalfunction. In this paper, the natural fermented lobster sauce from folk people in Linyi,Shandong province, was studied in detail to discover the dynamic changing on the microbialcommunities as well as the lobster sauce nutrient components during the fermentation process,and the physiological function of lobster sauce were expected to reveal. At the same time, therelated fermentation microbe were screened out and identified. The main results were asfollows:(1) Diversity analyses of fermentation flora of bacterium lobster sauceThe total DNA of lobster sauce from different fermentation time was extracted and thePCR amplification was carried out by the V3region primers of16S rDNA, named GC-357Fand517R. The160bp amplification products were separated by the denaturing gradient gel of30%to60%polyacrylamide. The PCR amplification was also performed on the total DNA oflobster sauce using the primers of27F-FAM and1492R. The amplification products weredigested by the enzyme Msp I and the digestion products were sequencing and OTU analyzed.The diversity index and abundance index kept steady in a low level, and the characteristics ofdominant flora were obvious in the fermentation process of bacterium lobster sauce byDGGE and T-RFLP analyses. The Bacillus Cohn acted as the dominate flora and thefermentation duration was7d.(2) Screening and identification of dominant flora in bacterium lobster sauceThe microbe in lobster sauce samples were separated counted on plate medium.11 bacteria were obtained and by thallus shape and colony characters, strain B1, B2, B3, B4, B5and B7were confirmed to be bacillaceae while NB1, NB2, NB3and NB4were non-bacillaceae, and strain C6was cocci. Strain B1, B2, B3, B4, B5, C6and B7were idealfermention bacteria by saline tolerance test and thermal endurance test. The identificationresults according to the physiological and biochemical characteristics as well as the molecularbiology indexes, were as follows: B1was Bacillus megaterium, B2was Bacillus coagulans,B3was Bacillus subtilis, B4was Bacillus licheniformis, B5was Bacillus kalodurans, B7wasBacillus amyloliquefaciens, andC6was Macrococcus caseolyticus.(3) Component analysis of bacterium lobster sauce in the process of fermentationThe amount of water, fat, protein, total sugar and raw fiber all declined during thefermentation of lobster sauce, while the amount of ash, pH, total acid, amino acid anddissociate amino acid all increased. There was no obvious change on the amount of totalamino acid.(4) Physiological function analysis of bacterium lobster sauceThe enzyme activity of cellulose maintained a low level in the solution of lobster saucefermentation while the enzyme activity of proteinase showed a tendency of increasing. Withthe fermentation duration, the transformation efficiency of genistein and daidzein, whichplayed a key role in physiological function, reached69.07%,54.54%, respectively. The MDAtest and SOD test showed the MDA value declined in the whole blood while the SOD activityincreased, which meant lobster sauce possessed an excellent anti-oxidation activity.