The present work was carried out to investigate factors influencing histamine formation by washed cell suspensions or cell-free extracts and growth in each condition on Photobacterium phosphoreum isolated from mackerel when stored at 0°C.
In the study of the effects of the reaction temperature on histamine formation and histamine forming activity, the optimum was at 35-40°C, and this was also observed at 50°C. Also while the growth was optimum at 25°C growth did not occur at 35°C. In regard to the effect of the reaction pH value, the activity was optimum at pH 5.5-6.5 and did not occur at pH 8.0, while growth was good at pH 5.5-8.0. In regard to the reaction NaCI concentration, the activity of the washed cell suspensions was optimum in 2-4% and low in 1 and 5%, and the activity of the cell-free extracts was optimum in the absence of NaCI and decreased with an increase of the concentration, while the growth was similar to the trend obtained on the activity of the washed cell suspensions. In regard to the reaction histidine concentration, activity increased quantitatively in the concentration above l00μg/ml and did not vary in that under 10μg/m/. In regard to the culture age, the activity was low in the early logarithmic phase, became maximal in the latest logarithmic phase, and decreased with the age of the culture. In regard to the presence of glucose in the growth medium, the activity increased in the presence of glucose and the activities with incubation time were different between the presence and the absence of glucose, while the pH value of the culture decreased with an increase of the activity. In regard to the oxygen tension of the culture medium, the activities were higher in anaerobic culture than in aerobic one, while growth was higher in the aerobic one.