Screening And Mechanism Off Cholesterol-lowing Lactobacillus

Overmuch intake of cholesterol in the blood and dietary has been recognized as a major riskfactor for coronary heart diseases and colon cancer. There has been an upsurge in finding ways tolower plasma cholesterol levels in human. Research proved that some prebiotics and some lacticacid bacteria could regulate lipid metabolism and reduce human serum cholesterol, but less hasbeen known of its effected factors and associated mechanisms.This paper could be divided intothree parts: isolation and identification of lactic acid bacteria strains with cholesterol-lowingability; mechanism of cholesterol lowing by latic acid bacteria and the ability of cholesterollowing of the strain combined with prebiotics; the cholesterol lowing ability of the strain insimulated gastric and intestinal tract.Firstly, we screened66bacteria strains from homemade pickle and the intestinal tract ofhuman and sea fish by selectivity spread plate. Based on the cholesterol-lowering ability,acid endurance and bile salt resistance of the strains,14strains of lactobacillus which hadcholesterol removing ability with removal rate ranging from7%to30%were harvested, amongthose candidate strains, one strain named MPCF7-3from human intestinal showed outstandingproperties, its ability of cholesterol removal in vitro could up to23.29%, and it could survivewell for2h in the environment with pH2.0and0.3%concentration of bile salt. This train thenwas identified as L. plantarum based on16S rDNA molecular biology assay.Then the study on the mechanism of cholesterol-lowing in vitro was carried out. The resultsshowed that L. plantarum MPCF7-3strain not only was able to precipitate and assimilatecholesterols, but also can incorporate cholesterols to cell membrane or cell wall, the rates ofcholesterol removal by the ways described above were56.78%,39.89%and3.35%respectively,which revealed that precipitate played the most important role. Resting and heat-killed cellswere able to remove little cholesterol by2.54%and1.4%respectively. The ability ofcholesterol lowing of the strain combined with prebiotics was also conducted, using the methodof Response Surface model/Box-Behnken analysis, conditions which have effect on thecholesterol removal of combination were determined and optimized, the optimal conditionswere: fructooligosaccharides concentration1.02%, sorbitol concentration1.50%and bile saltsconcentration0.17%. With this optimized condition, the cholesterol-removing was as high as34.04%，10.75%increased compared with that of no optimization. The result showed abovealso indicated that the Response Surface model could describe well the relation between cholesterol-lowing rate and bile salts, Fructooligosaccharides and sorbitol.At last of the paper the livability and the cholesterol-lowing ability of the L. plantarumMPCF7-3strain in simulated gastric and intestinal fluid were studied. The L. plantarumMPCF7-3strain concentration dereased from1010cfu/mL to108cfu/mL after treated withsimulated gastric fluid for2hours. The survival rate was5.14%after treated by simulatedintestines with prebiotics added for10hours, and and the cholesterol removal rate in vitro of theL. plantarum MPCF7-3strain was,17.54%, while the survival reate and the cholesterol removalrate was2.81%and3.45%respectively in the same environment but no prebiotics added, theresults indicated that binding prebiotics with the L. plantarum MPCF7-3strain has potential tolower serum cholesterol level of human.