Enzymochemical Study on growth of Psychrotrophs during Food Preservation in Refrigirator

从食物中分离的嗜冷菌中纯化了细菌生长必需的丙氨酸消旋酶。典型的嗜冷菌、荧光假单胞菌、嗜冷芽孢杆菌和嗜糖芽孢杆菌在30ºC以上的温度下培养1 h，酶活性明显失活，细菌在30ºC以上不能生长。因此，生长温度区域与酶的热稳定性是一致的。丙氨酸消旋酶的氨基酸组成和序列与其他嗜热菌和嗜热菌的丙氨酸消旋酶相似，可能适合于热稳定性的比较研究。来自嗜冷养动物的酶是耐热的，可以用变性剂和有机溶剂孵育灭活。特别是，20%的乙醇在0℃时也能显著灭活耐热酶。乙醇是一种有效的杀菌剂。

Alanine racemase essential to growth of bacteria was purified from psychrotrophs isolated from foods. The enzymesfrom typical psychrotrophs, Pseudomonas fluorescens, bacillus psychrophilus and Bacillus psychrosaccharolyticus were markedly inactivated when incubated at over 30ﾟC for 1 h, and the bacteria could not growat over 30ﾟC.Thus, the region of growth temperature were consistent with the thermostability of the enzymes. Since the amino acid composition and sequence were similar to those of other alanine racemases from mesophiles and a thermophile, alanine racemase may be suitable for comparative study on thermostability. The enzymes from psychrotrophs were thermolabile, and inactivated by incubation with denaturants andorganic solvents. Especially, 20% ethanol markedly inactivated the thermolabile enzymes even at 0ﾟC.Ethanol was effective as a sterilizer to psychrotrophs.