Koka R A, Weimer B C
Center for Microbe Detection and Physiology, Department of Nutrition and Food Sciences, Utah State University, Logan 84322-8700, USA.
J Dairy Res. 2001 Feb;68(1):109-16. doi: 10.1017/s0022029900004647.
Many psychrotrophic bacteria contaminating raw milk produce phospholipase that withstands pasteurization and UHT treatments. This enzyme acts on the milk fat globule membrane and exposes triacylglycerides to the action of lipase. Phospholipase production by various isolates of Pseudomonas was investigated. The isolates were cultured aerobically at 8 degrees C in nutrient broth, McKellar's minimal salts medium, Chrisope's medium, and skim milk. Each strain produced phospholipase during the 50 h incubation. Enzyme production varied significantly (P < 0.001) with strain and growth medium. Strains varied significantly (P < 0.001) in their enzyme production in each medium and during the incubation time as well. Strain, incubation time, and the growth medium significantly influenced (P < 0.001) heat stability of the enzyme activity. Pasteurization reduced the activity, but did not eliminate it in skim milk.
许多污染生牛奶的嗜冷菌会产生能耐受巴氏杀菌和超高温瞬时灭菌处理的磷脂酶。这种酶作用于乳脂肪球膜，使甘油三酯暴露于脂肪酶的作用之下。对各种假单胞菌分离株产生磷脂酶的情况进行了研究。这些分离株在8℃下于营养肉汤、麦凯勒氏基本盐培养基、克里索普培养基和脱脂乳中进行需氧培养。在50小时的培养过程中，每个菌株都产生了磷脂酶。酶的产生因菌株和生长培养基的不同而有显著差异（P<0.001）。在每种培养基中以及培养期间，菌株产生酶的情况也有显著差异（P<0.001）。菌株、培养时间和生长培养基对酶活性的热稳定性有显著影响（P<0.001）。巴氏杀菌降低了脱脂乳中的酶活性，但并未将其消除。
