Paul M, Somkuti G A
Eastern Regional Research Center, Agricultural Research Service, US Department of Agriculture, Wyndmoor, PA 19038, USA.
Lett Appl Microbiol. 2009 Sep;49(3):345-50. doi: 10.1111/j.1472-765X.2009.02676.x. Epub 2009 Jun 15.
To analyse the effect of cell-associated peptidases in yogurt starter culture strains Lactobacillus delbrueckii ssp. bulgaricus (LB) and Streptococcus thermophilus (ST) on milk-protein-based antimicrobial and hypotensive peptides in order to determine their survival in yogurt-type dairy foods.
The 11mer antimicrobial and 12mer hypotensive milk-protein-derived peptides were incubated with mid-log cells of LB and ST, which are required for yogurt production. Incubations were performed at pH 4.5 and 7.0, and samples removed at various time points were analysed by reversed-phase high-performance liquid chromatography (RP-HPLC). The peptides remained mostly intact at pH 4.5 in the presence of ST strains and moderately digested by exposure to LB cells. Peptide loss occurred more rapidly and was more extensive after incubation at pH 7.0.
The 11mer and 12mer bioactive peptides may be added at the end of the yogurt-making process when the pH level has dropped to 4.5, limiting the overall extent of proteolysis.
The results show the feasibility of using milk-protein-based antimicrobial and hypotensive peptides as food supplements to improve the health-promoting qualities of liquid and semi-solid dairy foods prepared by the yogurt fermentation process.
分析酸奶发酵剂德氏乳杆菌保加利亚亚种（LB）和嗜热链球菌（ST）中的细胞相关肽酶对基于乳蛋白的抗菌肽和降血压肽的影响，以确定它们在酸奶类乳制品中的存活情况。
将11聚体抗菌肽和12聚体降血压乳源肽与酸奶生产所需的处于对数中期的LB和ST细胞一起孵育。在pH 4.5和7.0条件下进行孵育，通过反相高效液相色谱（RP-HPLC）分析在不同时间点取出的样品。在pH 4.5时，在ST菌株存在下肽大多保持完整，而暴露于LB细胞时会被适度消化。在pH 7.0孵育后，肽的损失发生得更快且更广泛。
当pH值降至4.5时，可在酸奶制作过程结束时添加11聚体和12聚体生物活性肽，以限制蛋白水解的总体程度。
结果表明，将基于乳蛋白的抗菌肽和降血压肽用作食品补充剂，以改善通过酸奶发酵工艺制备的液体和半固体乳制品的促进健康品质是可行的。
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