Enzymochemical Study on growth of Psychrotrophs during Food Preservation in Refrigirator

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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.