Microbial community structure and its dynamic analysis of pickled mustard tuber during a low-salt processing

Pickled mustard tuber is a traditional Chinese food preserved by high-salinity pickling process. A cleaner production technique of pickling mustard tuber process has been widely focused on the pickled fermentation with a low salt concentration. The objective of this present study was to determine the microbial community structure and its predominant functional species by single strand conformation polymorphism (SSCP) profiles under the optimizing pickling conditions with low salinity. Effects of SSCP conditions on gel electrophoresis assay as well as changes of lactic acid bacteria (LAB) population were also investigated. Results: Twenty two percent of gel concentration and addition of 6% glycerol in gel preparation for electrophoresis separation were ideal conditions for SSCP analysis of microbial community in pickled mustard tuber. The pH value in leaching liquid was descending throughout the pickling process and the total LAB population increased, reached the peak of 7.51 log cfu mL^-1 at day 10 by plate counting then decreased gradually until to a stable level. With the optimal SSCP technique, 11 distinct dominant bands were obtained throughout the fermentation process of mustard tuber. Based on the sequence comparison the results showed that Leuconostoc mesenteroides was the predominant microorganism in the initial stage of fermentation. Then the Lactobacillus plantarum and Lactobacillus brevis appeared quickly. At the later stage, the predominant species were Lactobacillus plantarum and Lactobacillus versmoldensis. Conclusions: SSCP technique is a feasible method for microbial community analysis in pickled mustard tuber. Gel concentration and addition of glycerol in gel for electrophoresis operation had influences on the SSCP pattern performance for microbial community analysis of pickled samples. The contribution of some dominant LAB species was confirmed by SSCP method under the optimized processing condition of pickled mustard tuber.