Detection of Cholesterol Esterase in Leuconostoc Dextranicum Isolated in Foods

Abstract

Streptococcus thermophilus was isolated from ferment foods in Vietnam. This strain was determined by API 50 CHL (BioMerieux). Interestingly, we have detected and characterized the enzyme called cholesterol esterase that will be used in cholesterol diagnostic and treating the cholesterol ester storage disease in women. After culturing, the free cell supernatant was precipitated with 60% ammonium sulfate and resuspended in distilled water. After dialysis, the supernatant had been titrated with 1M sodium hydroxide and detected by thin layer chromatography (TLC). The detection was based on the determination the free fatty acid that was the product of cholesterol ester hydrolyzation by cholesterol esterase. The color changed in titration and the spot appearance compared with the standard in TLC showed the presence of cholesterol esterase. The cholesterol esterase production was also optimized in different conditions containing vitamin D, and palmitic acid as the substrates of cholesterol. The study showed that Streptococcus thermophilus should be supplied in ferment food as yogurt in order to improve the health for human.