Screening Of Lactobacillus For Lowering Cholesterol And Whole Genome Sequencing Analysis

Lactobacillus plantarum is a kind of probiotics which have a lot of good effect to the body, strain typing in the genus Lactobacillus, Gram-positive bacteria,and it has variety of functions such as maintaining the balance of intestinal flora,Reducing the cholesterol in vivo and in vitro and improving the body immunity. In this study, we get the lactic acid bacteria by isolating and purification from MRS and M17 culture medium, and the lactic acid bacteria was treated by artificial gastric juice(p H2.5)and bile salt solution(0.3%),by using gradient dilution plate counting method, we selected 22 acid and bile salt tolerance strains,the Lactobacillus plantarum Y-9 showed the highest acid and bile salt tolerance,up to125%.By cholesterol lowering function study using the method of in vitro screening of acid and bile salt tolerance during 8 strains, we found Lactobacillus plantarum Y-9 showed strong assimilate cholesterol ability, the amount of reducing cholesterol was 88.79mg/L, and the cholesterol removal rate was 41.63%,so the Lactobacillus plantarum Y-9 was the purpose of the strains that we want.Based on the model of experimental hyperlipidemia rat, we observed the effects on rats blood lipid level by different gavage group deal with Lactobacillus plantarum Y-9(Living bacteria group, dead bacteria group, high-fat group and normal control group). Animal studies showed the rat‘s(gavaged after 28 days) total cholesterol(TC), low-density lipoprotein cholesterol(LDL-C), high density lipoprotein cholesterol(HDL-C) and triglyceride(TG) decreased significantly(P < 0.05), so we believe the Lactobacillus plantarum Y-9 has the auxiliary function of reducing blood fat, particularly to hypercholesterolemia. In order to parsing lactobacillus Y-9 on genome level and improving genome to get strains with stronger assimilate cholesterol ability, we tested the whole genome sequencing of lactobacillus Y-9using high throughput technology. The sequencing depth was 100 X, assembly length was 3.15Mb(Scaffold N50=247kb, Contig N50=209kb).The annotation gene amount was 3179, repetitive sequence length was 130 KB, accounting for4.13% of the genome length. Gene function enrichment analysis showed gene significantly enriched to amino acid transport and metabolism, energy transformation and immune defense. Gene family evolution analysis showed the gene families related to plant lactobacillus, proteolytic systems, sugar metabolism and extracellular polysaccharide synthesis expanded significantly(P<0.05). In addition, collinearity analysis of Lactobacillus plantarum Y-9 and ST-III and JDM1 genome showed that the genome assembly of Lactobacillus plantarum Y-9is integrated. We compared and analyzed the whole genome of three strains(Lactobacillus plantarum Y-9 and ST-III and JDM1). This result showed lactobacillus plantarum has conservative genome organizational structures. In a word combination the studies of Lactobacillus plantarum Y-9 in vitro and animal,analysis with its genome structure characteristics, metabolic diversity, evolution and collinearity showed the strain has the function of lowering cholesterol significantly and the potential to develop functional products.