| Probiotics can resist the adverse conditions of the human gastrointestinal tract,colonize and adhere to the intestinal epithelial cells,participate in the body’s immune regulation,improve the intestinal barrier,and enhance the body’s antioxidant capacity.Probiotics play an active role in alleviating the body’s oxidative damage and preventing degenerative diseases.This research aimed to isolate human-derived probiotics,evaluate the probiotic properties of probiotics through a series of in vivo and in vitro tests,and screen out human-derived probiotic strains with antioxidant properties and multiple probiotic properties.This study lay a foundation for further research and application on anti-oxidant mechanism of these probiotics.The main results are presented as follows:1.Fifteen strains of Bifidobacteria,14 strains of lactic acid bacteria,and 3 strains of Bacillus were isolated and identified from healthy human feces.9 strains were screened out by measuring the DPPH free radical scavenging rate and anti-lipid peroxidation ability of the intact-cell(IC)and cell-free extracts(CFE)candidate strains of probiotics,namely BL T37 a,BL BX16,BP R3,BA T29,BB MN8,BP H4,EAE BN6,EAE BJ2 and EFA MC4.2.The safety and probiotic properties of 9 candidate probiotic strains were evaluated in vitro.The results showed that 9 candidate strains of human-derived probiotics showed no hemolysis,produced no harmful metabolites,and had varying degrees of sensitivity to 12 antibiotics.Through acid and bile salt resistance test,bacteriostasis test,bacterial surface property test,cell adhesion test and adhesion test of inhibiting pathogenic bacteria,Bifidobacterium longum T37 a and B.pseudocatenulatum R3 were screened out.There is a better survival rate under the environment of p H=3.0 and 0.3% bile salt.9 strains of intestinal pathogenic bacteria have different degrees of bacteriostasis,and a higher cell adhesion rate,which can be through competition,exclusion and replacement ways to inhibit the adhesion of Escherichia coli ATCC 43888,Staphylococcus aureus ATCC 6538 and Salmonella typhimurium ATCC 14028.3.Different doses of T37 a and R3 were used to gavage D-galactose aging model mice for studying the oxidant properties of probiotics in vivo,and vitamin C was used as a positive control.The results showed that T37 a and R3 have a repairing effect on aging mice.Different doses of T37 a and R3 can reduce varying degrees oxidative damage and increase the index of immune organs,respectively.Observing liver and intestinal tissues,it is found that probiotics can significantly increase the length of the villi of the duodenum and ileum(P<0.05,P<0.01),and the V/C value of the ileum increased significantly(P<0.05),indicating that supplementing with probiotics can alleviate the oxidative damage of liver and intestinal tissues and repair the morphology of mucous membranes.Through the detection of serum immunoglobulins and cytokines,and the antioxidant indicators in liver tissue homogenate,the Ig G1 level of mice in the T37 a high group increased significantly(P<0.01),indicating that B.longum T37 a can upregulate the immune function of mice.T37 a and R3 significantly decreased the content of IL-6(P<0.05,P<0.01),and significantly increased the content of IL-10,indicating that probiotics can relieve inflammation caused by aging.T37 a and R3 can increase the content of AOC(P<0.05,P<0.01),SOD and GSH-Px(P<0.05),and significantly reduces the level of MDA(P<0.05,P<0.01)in liver tissue,indicating that probiotics can improve the antioxidant capacity of aging mice.4.Based on 16 S r DNA sequencing technology,analysis of the effect of probiotics on the intestinal flora of aging mice,the results showed that,T37 a and R3 can regulate the abundance and diversity of the intestinal flora of aging mice,but will not change the advantages of the intestines flora.Probiotics will reduce the phylum Bacteroides and increase the phylum Firmicutes,and will increase the proportion of beneficial bacteria. |
