Screening And Comparative Analysis Of Cholesterol-lowing Lactobacillus

With the improvement of people's living standards,people's diet structure has undergone major changes,resulting in excessive intake of cholesterol,hyperlipidemia,coronary heart disease,arteriosclerosis and other cardiovascular diseases.These diseases have seriously jeopardized human health,and research on how to reduce cholesterol intake and lower blood cholesterol levels has received increasing attention.The aim of this study was to screen safe and highly efficient lactic acid bacteria strains with a food source that degrades cholesterol,and to provide a theoretical basis for the development of new lactic acid bacteria agent or low cholesterol foods.The main findings are as follows:1.Through the evaluation of in vitro cholesterol scavenging ability,bile salt hydrolase activity and gastrointestinal fluid tolerance of 34 tested strains,five potential strains were screened,which were 60,JQIII-15,15-12,71,JQIII-13 respectively.Through morphology,Mérieux API50 CHL carbon source metabolic profile,16 S rDNA molecular identification means,combined with the national list of edible strains,the strain 60(,Lactobacillus paraplantarum)was eliminated,the repetitive strain JQIII-15 was eliminated.Finally,three strains were obtained,which were 15-12,71,and JQIII-13,respectively.2.Three strains of lactic acid bacteria(71?15-12?JQIII-13)were used to study the adhesion of HT-29 cell lines and the antibacterial activity against five common human pathogens.The results showed that all three strains had good adhesion to HT-29.The highest adhesion index of JQIII-13 B was 8.22 CFU / cell.The bacteriostasis experiments showed that the supernatant of MRS fermented and 80 ? water bath supernatant in three strains could show specific antibacterial activity,PH adjusted supernatant were not bacteriostatic effect.The results showed that all three strains could inhibit S.aureus and Enterobacter cloacae,JQIII-13 and 15-12 had inhibitory effects on Pseudomonas aeruginosa,only 15-12 had inhibitory effect on Escherichia coli,three strains can not inhibit the growth of Candida albicans.JQIII-13 and 12-15 had better antibacterial activity,especially 12-15 was a probiotic with broad-spectrum antibacterial activity.3.The safety of three strains of lactic acid bacteria,71,15-12 and JQIII-13,was evaluated.The phenotypes of metabolites(biogenic amines,D-lactic acid)and harmful metabolic enzymes(nitroreductase)and resistance to 13 antibiotics were determined.It was found that none of the three strains produced metabolites of biogenic amines and nitroreductase,and a certain amount of D-lactic acid was produced in the MRS medium,but the yield capacity was within the safe range.Antibiotic resistance test results showed that 15-12 and JQIII-13 to 13 kinds of antibiotic resistance levels meet the EFSA standard.However,the level of resistance to both erythromycin and clindamycin of 71 was above the safety threshold(MIC valu),and the strain did not meet the screening requirements.4.The cholesterol-lowering effect of two strains(15-12?JQIII-13)was evaluated by hyperlipidemia SD rat model.The results showed that the two lactic acid bacteria could not only reduce the level of serum TC and TG of the rats with hypercholesterolemia,but also decrease the levels of TC and TG in the liver and promote the excretion of TC and TBA from feces.15-12,JQIII-13 are two probiotic strains with development and application prospect.