Enzymochemical Study on growth of Psychrotrophs during Food Preservation in Refrigirator

从食品中分离的耐冷菌中纯化了细菌生长所必需的丙氨酸消旋酶。典型的耐冷菌荧光假单胞菌、嗜冷芽孢杆菌和解冷糖芽孢杆菌在30 ℃以上培养1h后，其酶活性明显失活，细菌在30 ℃以上不能生长，其生长温度范围与酶的热稳定性相一致。由于氨基酸组成和序列与来自嗜温菌和嗜热菌的其他丙氨酸消旋酶相似，丙氨酸消旋酶可能适合于热稳定性的比较研究。耐冷菌的酶是不耐热的，与变性剂和有机溶剂孵育会使其失活。特别是，20%乙醇即使在0 ℃也能显著灭活不耐热酶。乙醇是一种有效的耐冷菌灭菌剂。

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.