Study On Screening Of ACE Inhibitory Activity Of Lactic Acid Bacteria And Its Fermentation Characteristics In Milk

The 52 strains of Lactic acid bacteria isolated from traditional fermented milk in Xilinguole and Bayannaoer area of Inner Mongolia, China, were evaluated to ACE-inhibitory activity, resistance of bile salts, simulated and gastrointestinal juice, and the selected strains were determined to growth characteristics in milk, the ACE inhibitor was isolated from milk and its stabilities were studied. The main results were as follows: The 22 strains of lactic acid bacteria were selected by higher of ACE inhibitory activity (higher than 33%). then 6 strains were selected for higher tolerance (more than 80%); and 3 strains of Lactobacillus helveticus 130B4, Lactobacillus casei 325M2, Lactobacillus delbrueckii ssp. lactis QS306 were patient to the simulated gastric juice (pH2.0, 3h of incubation), then through the gastrointestinal juice (pH8.0, 24h of incubation), rate of incrense were 117%, 28.30% and 39.55%. The selected strain Lactobacillus helveticus 130B4 was growing slowly in skim milk for 36h, the acidity was 0.8%, after 72h, the acidity was 1.85%, the total bacteria counts could reach 1.0×109 CFU/g. The acid production ability, protein decomposition, ACE inhibitory activity of this strain could be promoted by yeast leaching, soybean peptide, nucleic acid related substances (adenine, guanine, uracil and xanthine). Three fractions (A, B and C) were collected by Sephadex G15 from fermented milk, and the ACE inhibitory activity of fraction B was the highest ((69.92±0.79) %), and its IER ((88.06±0.0728)g/L) was obviously higher than other fractions (P<0.05). The resistance of purified inhibitory fraction to changes in their ACE inhibitory activity before and after treatment with heat and gastrointestinal proteases were examined. The ACE inhibitory activity of fraction B was completed preserved after the heat treatment. The ACE inhibitory activity was degreased to 98.33% at 100℃for 20min, and 73.81% at 110℃for 20min. The ACE inhibitory activity of fraction B was completed preserved after the pepsin and trypsin.