Safety Evaluation Of Pediococcus Pentosaceus Adsorbed With Lead And Metagenomic Analysis Of Intestinal Microorganisms

Lead is a heavy metal element that is not degraded by the environment for a long time.The accumulation of trace amounts through the food chain will cause irreversible harm to the human body.Its pollution is one of the hot issues of food safety.The use of food-grade lactic acid bacteria to adsorb heavy metals is simpler,more efficient and free from secondary pollution than traditional methods.However,when a lactic acid bacteria with no history of safe consumption is used in food,safety evaluation must be carried out.In this study,the in vitro safety test was carried out on 4 strains of Pediococcus pentosaceus screened by the previous research group with the ability to adsorb lead;the toxicological test was carried out on the strain 10-a-1 with the highest safety;1 The effect of entering the host’s gut on the host’s gut microbial community and function,as well as the differences between the experimental group and the control group,provide a basis for the application of strain 10-a-1 in the field of heavy metal adsorption.In this thesis,the growth curves of 4 strains of Pediococcus pentosaceus that were isolated and screened from Baotou City,Inner Mongolia Autonomous Region in the early stage with the ability to tolerate lead were measured,and the Pb2+ adsorption capacity of the 4 strains of Pediococcus pentosaceus was determined.Between-90.95%.The in vitro safety test of 4 strains of Pediococcus pentosaceus was carried out.In the test of harmful metabolites,4 strains were negative in amino acid decarboxylase(lysine,phenol,group,ornithine);the indole test of strain F-e-3,nitrate reductase test is positive;strain 10-a-1 has no ability to decompose arginine into spermine,and does not produce D-lactic acid;gelatin liquefaction test shows that 4 strains do not have gelatin liquefaction ability;drug resistance The results of sex test showed that 4 strains were moderately sensitive to erythromycin,resistant to the other 7 antibiotics and had no plasmids;the results of hemolysis test showed that strain 9-b-1 had β-hemolysis.In conclusion,the results of the in vitro safety test evaluation showed that only Pediococcus pentosaceus 10-a-1 was the safest strain.Toxicological test was carried out on Pediococcus pentosaceus 10-a-1,which was the safest,and the upper-lower limit method was used in the acute toxicity test of mice for 7days.After gavage,the central nervous system,body movement,and autonomic nervous system of the mice were all normal,and there was no risk of bacterial transfer.There was no significant difference in biochemical parameters(γ-GD,ALT and AST)and intestinal(colon,cecum,ileum)morphology,and 6.667 mg/g·BW was determined as a non-toxic dose.In genotoxicity,the default measurement gradient coefficient was 3.2,and the high,medium and low dose groups were 6.667,1.850,and 0.583 mg/g·BW,respectively.There was neither significant difference nor dose-response relationship between the experimental group and the negative control group in the erythrocyte micronucleus test,indicating that Pediococcus pentosaceus 10-a-1 had no ability to cause germ cell and bone marrow cell malformations in mice.In the 28-day oral toxicity test,the production performance,viscera-to-body ratio(heart,kidney,spleen,liver),blood biochemical indexes(γ-GD,ALT and AST)and intestinal(colon,cecum,ileum)morphology of mice No significant difference and no dose-response relationship.Through metagenomics analysis of the feces of 3 male mice in each of the experimental group and the normal saline group that were given Pediococcus pentosaceus10-a-1,the results showed that the intestinal microbes in the experimental group and the control group were at the phylum level in 4 periods.The relative abundances of Firmicutes,Bacteroidetes,Actinobacteria,Deferriobacteria and Proteobacteria were all in the top 5.The relative abundance of Myxospira increased significantly in the E3 and E4 stages of the experimental group with the increase of the gavage time of the experimental group.The top 3 functional categories of intestinal metagenomes in the experimental group and the control group were carbohydrate metabolism,amino acid metabolism,cofactor and vitamin metabolism.Compared with the control group,the abundance of Bacteroidetes in the experimental group showed an increasing trend with the increase of gavage days,while the abundance of Firmicutes in the experimental group decreased with the increase in the gavage days compared with the control group.There were significant differences in 15 genera in the group gut microbes at the genus level.At the species level,the E4 period had the highest number of characteristic microorganisms compared with other periods.In terms of function,based on LEf Se analysis,it showed that a total of 20 MAPs,18 GOs,and 12 CAZys were significantly different between the experimental group and the control group,and the pathways with different KEGG functions in the E4 period were the most compared with other periods.