Impact Of Old And Fresh Brine On The Sichuan Kimchi Lacticacid Bacteria Community

In traditional Sichuan pickles, Lactic acid bacteria is the most important kimchi microbial population. Lactic acid bacteria have an important role to optimize the production process of the conventional method in the fermentation process. In this thesis, firstly, three vegetable Sichuan pickles(cabbage, radish and cowpea) were fermented by the traditional methods in the different salt concentration(4%,6% and 8%). The total lactic acid bacteria and titratable acid concentration were detected in the whole fermentation process. Secondly, total lactic acid bacteria community structure and titratable acid concentration were compared between old and fresh fermentation in the best salt content. The research result as follow:1. This study used three fresh salt concentrations (4%,6%,8%) to ferment cabbage, radish and cowpea. The concentration of lactic acid bacteria increase in the first period and then decrease at the end of period. Lactic acid bacteria reach the maximun concentration at the 7th day. Lactic acid bacteria in 6% salt growth faster than others, and has higher productivity of titratable acid concentration. Different vegetables have the various bacteria community in the fermentation process. Cabbage has higher bacterial growth rate and productivity of titratable acid concentration than radish and cowpea.2. Comparing old and fresh brine (6%,salt concentration) to ferment cabbage, radish and cowpea, respectively. The old brine has higher bacterial growth rate and productivity of titratable acid concentration than fresh brine, which lactic acid bacteria reach the maximun concentration at the 3rd day, while fresh brine reach the max at 7th day. The average increase concentration of titratable acid is 0.272 mg/mL in old brine, which higher than that of fresh brine (0.216 mg/mL). There are small difference of lactic acid bacteria and titratable acid concentration was between cabbage, radish and cowpea in the old brine.3. PCR-DGGE was used to analysis lactic acid bacterial diversity and community dynamics in the fermenting process of cabbage, radish and cowpea between fresh and old 6% salt brine. The richness and diversity index has increase in the whole process both fresh and old brine, and old brine has higher index than fresh brine and community of old brine has more stable dynamics than old brine. The cloning analysis indicated the distribution of predominate lactic acid bacterial:Lactobacillus(36-3%)>Pediococcus (15-20%)> Leuconostoc (5-10%). In the whole fermentation process, the relative concentration of Lactobacillus displayed the increasing tend while Leuconostoc displayed the slowly decreasing trend and Pediococcus kept stable, and fresh brine has more significant shift.4. Traditional heterotrophic plate counts was used to separate typical lactic acid bacteria in the old brine fermentation. Three bacteria isolated, and 16S rDNA sequencing analysis showed that these three bacteria is the Weissella cibaria, the Leuconostoc citreum and Lactobacillus plantarum. These result was similar the DGGE clone.