Screening Of Cholesterol-degradation Lactic Acid Bacteria And Effects Of Different Ions On Cholesterol Degradation

Cardiovascular diseases and liver disorders caused by hypercholesterolemia have now become one of leading factors that seriously influence people's health around the world.Recent reports revealed that a reduction in the level of serum cholesterol was associated with probiotics,such as Lactobacillus and Bifidobacterium.Lactic acid bacteria?LAB?are common microbes used as probiotics,which are members of the commensal bacteria in the gastrointestinal tract of human and animals.They are the most important bacteria used in food fermentations because of their long and safe use as starter cultures in fermented products.Various studies in vivo have shown that some Lactobacilli can lower cholesterol and many kinds of Lactobacillus cultures exerted potential hypocholesterolemic activity.Therefore,the potential hypocholesterolemia activity of Lactobacillus has led to an increasing attention to the possible application.In order to obtain high efficient cholesterol degradation lactic acid bacteria?LAB?and research the effect of common metal ions on their cholesterol decomposition function,this study attempted to isolate LAB by dissolved calcium ring method on MRS plate with 1%CaCO₃ from sheep blood,fish roe,fatty pork and bacon which are rich in cholesterol.These isolates and other 4 strains identified as LAB and saved in our laboratory were then carried out to detect their cholesterol degrading ability and screening higher efficient cholesterol-degradation strains.Following that,the effects of different metal ions on cholesterol-loweringofselectedstrainswereinvestigatedinvitro.The cholesterol-degradation percentages of 14 suspected LAB strains isolated from food samples and 4 strains LAB in our lab were analyzed.Two higher efficient cholesterol degradation strains,1 strain of Lactobacillus plantarum?Lpl?and 1 strain of Lactobacillus rhamnosus?Lrh?were chosen out to research the effects of anions and cations on their cholesterol-reduction.The main conclusions were as follows:?1?Different cations presented different influences on cholesterol degradation efficiency and efficacy of two selected LAB strains.The cholesterol degradation efficiency of two strains were enhanced only under additional 0.02 N concentration of Ca²⁺,but decreased with the increase of other cations concentration.However,the cholesterol efficacy of both Lrh and Lpl were highest under extra 0.02 N of Li⁺,K⁺,Ca²⁺and Al³⁺of MRS-CHOL medium and gradually reduced with the concentration increase.Meanwhile,the cholesterol efficacy of two strains always decreased with the increase of concentration of additional Mn²⁺,Cu²⁺and Fe³⁺.?2?Different anions presented different influences on cholesterol degradation efficiency and efficacy of two selected LAB strains.The cholesterol degradation efficacy of two strains were enhanced only under additional 0.02 N concentration of SO₄^2-and PO₄^3-,but decreased with the increase of other anions concentration.When additional concentration of Cl^-,SO₄^2-and PO₄^3-in Lrh and NO₃^-,SO₄^2-and PO₄^3-in Lpl were 0.02N respectively,the cholesterol efficacy were highest and gradually reduced with the concentration increase.The cholesterol degradation efficacy of two strains were enhanced only under additional 0.02 N concentration of Ca²⁺,but decreased with the increase of other anions concentration.Meanwhile,the cholesterol efficacy of two strains always decreased with the increase of concentration of additional other anions.?3?The optimal culturing condition of Lrh and Lpl was:glucose 2%,soy peptone addition 1%,twain 0.1%,initial pH of the medium 6.0.Two strains optimized production of bile salt hydrolase activity were 1.13 times and 1.11 times before.