Bacterial Diversity Of Sichuan Pickle And Screening Of Strains With Potency For Degrading Biogenic Amines

Sichuan Pickle is outstanding representative of the fermented vegetables in our country, and contains abundant microbial resources. Biogenic amines(BAs) can be found naturally in a wide range of foods, especially fermented foods. If BAs are ingested in high concentrations, these compounds can cause damage to human health. Thus, it is particularly important to control the content of biogenic amines in fermented foods, and the best strategy is to eliminate the BAs through the use of microorganisms. For these reasons, this study first investigated the bacterial deversity of the Sichuan pickle and changes during the fermentation by Illumina high-throughput sequencing. Basing on the screenin index of having the potential as a starter, tolerating the conditions of human stomatch and effectively degrading the BAs, one strain of Lactobacillus plantarum was isolated. It was also proved that the strain’s ability to degrade BAs was related to sufⅠgene.According to the sensory evaluation of 20 samples of Sichuan homemade pickles, 3 samples with higher scores were selected for bacterial diversity analysis. The results showed that Sichuan Pickles consisted Lactobacillus genus as the most, accounting for 76-89%. During the vegetable fermentation started by Sichuan Pickles water, the abundance of Weissella was 74.5% at the beginning of the fermentation but then decreased and remained stable at about 10%. After the start of the fermentation, the Lactobacillus strains took place to be the dominationated bacteria, with a content of 80-85%. It’s indicated that during the fermentation, Weissella was the starter and Lactobacillus dominated the whole process. In the meantime, Sichuan pickles were proved to be excellent microbial resources of separating and screening for probiotics, and developing of lactic acid bacteria(LAB) as starter for fermented foods.In view of the LAB isolated from Sichuan Pickles, 5 strains of L. plantarum and 1 strain of L. buchneri were selected for significant degration of biogenic amines. L. plantarum M6 could degrade tryptamine(Try), 2-phenylethylamine(Phe), putrescine(Put), cadaverine(Cad), histamine(His), tyramine(Tyr), spermideine(Spd) and spermine(Spm) for 6.74%, 38.94%, 63.90%, 53.12%, 96.69%, 32.81%, 85.68% and 92.15%, respectively. And the strain degraded the whole BAs for 67.33%. Then experiment was taken to find the relationship between BAs degration and sufⅠgene, which was reported related to degrade BAs from a strain of L. plantarum. The sufⅠgene was found in the 5 selected strains of L. plantarum but not in the strain of L. buchneri, so it’s speculated that there were some other genes playing the role of BAs degration in L. buchneri. While the 5 selected strains of L. plantarum presented defferences in degration ability, the whole sufⅠgenes from 5 strains were sequenced and their products were deduced from the gene orders, and presented. The result showed that 4 of the strains had a different site according to their sufⅠgene’s expression product, that was why they showed difference on BAs degration. At the same time, L. plantarum M6’s sufⅠgene was connected with E. coli expression vector p ET-28 b to get recombinant plasmid p ET-28b-sufⅠ, and then the recombinant plasmid p ET-28b-sufⅠwas expressed into E. coli host bacterium BL21. After separation and putification of the expressed product from the culture solution, SufⅠprotein was finally got. The protein showed degration of 58.07%, 61.49%, 75.23%, 75.79%, 81.07%, 58.57%, 87.38% and 94.89% for Try, Phe, Put, Cad, His, Tyr, Spd and Spm, respectively. And the percentage for all BAs degration was 73.19%. So this study resulted in that L. plantarum M6 was good at degrading BAs, which was closely related to its sufⅠgene.This paper systematically studied the bacterial diversity and dynamic changing regularity of Sichuan pickle, and selected an excellent LAB for good degration of BAs, named by L. plantarum M6. Futhermore, the gene for BAs degration was determined and related protein was separated. The results provide not only the reference for developing good starter for fermented food, but also a good strain and functional protein. It has a certain theoretical significance and the practical value.