Study On Cholesterol Removal By Lactobacillus Acidophilus And Its Mechanism

Cholesterol is an important and indispensable substance for human body, which maintains human’s normal physiological function, however, excessive cholesterol intake may cause incidence of cardiovascular and cerebrovascular diseases increase. Therefore, the maintenance of human serum cholesterol in the normal rang has important significance. Many investigations indicated that lactic acid bacteria and other probiotics had an action to decrease cholesterol concentration, however, the mechanism is inconclusive now. This paper studied on cholesterol reduction by two Lactobacillus acidophilus strains and its mechanism, the main results were as follows:The cholesterol-lowering action of Lactobacillus acidophilus la1and la2increased with culture time, the better cholesterol-lowering rate was at24h,53.11%and42.92%respectively, which assimilation were42.13%and39.05%, co-precipitation of10.59%and5.37%. Thus, the cholesterol-reducing effect of la1and la2were the result of assimilation-based multi-faceted interaction. In vitro the cholesterol-lowering effect of lal and la2were influenced by various factors, including the type of bile salt, bile salt concentration, inoculum size and so on. Learned by univariate analysis, bile acid was best for lal and la2reduced cholesterol, the better amount of cholesterol reduction could be reached when the addition of bile salt was0.2%, inoculum size of5%, respectively.The surface hydrophobicity of Lactobacillus acidophilus la1and la2measured by MATH method suggested that both la1and la2had a good surface hydrophobicity; the SEM of la1and la2results showed that cholesterol could be absorbed to the surface of them, and precipitated with bacteria under the centrifugal condition; cholesterol removed by la1and la2had a close relationship with cell growth, compared to dead cells and resting cells, the cholesterol reduction rate of normal living cells were significantly higher, which was the interaction of assimilation and co-precipitation; cells cultured in the presence of cholesterol were more resistant to ultrasonication than control group, this might be bacteria absorbed cholesterol to cells; further determination on intracellular fatty acid by using GC-MS, showed that total saturated acids of the cells in the presence of cholesterol reduced to13.55%and17.87%,and and unsaturated acids of the cells increased to53.73and53.91%, respectively, these suggested that intracellular lipid profile changed, cholesterol indeed absorbed into cells.Compared to crud enzyme of bile salt hydrolase of la1, the special activity were47.82U/mg and 115.85U/mg, the purification factor were4.46fold and10.82fold respectively, after ammonium sulfate precipitation and DEAE-Sepharose CL-6B column chromatography; the result of SDS-PAGE gel electrophoresis of bile salt hydrolase showed that its molecular weight were about43KD; studied on part of the enzymatic properties of bile salt hydrolase purified, the results showed that the optimum temperature was40℃, the optimum pH was6.0, Fe3+, Ca2+, Mg2+, Mn2+,Zn2+all had activation on bile salt hydrolase, among which the activation of Fe3+was strongest, Na+,K+had no activation effect on bile salt hydrolase, while Cu2+and Ba2+had strong inhibition.