FACTORS INFLUENCING HISTAMINE FORMATION B Y PSYCHOTROPHIC LUMINOUS BACTERIA PHOTOBACTERIUM-PHOSPHOREUM

The present work was carried out to investigate factors influencing hi stamine formation by washed cell suspensions or cell-free extracts and growth in each condition on Photobacterium phosphoreum isolated from mackerel when stored at 0-degree-C. In the study of the effects of the reaction temperature on histamine formation and histamine forming act ivity, the optimum was at 35-40-degrees-C, and this was also observed at 50-degrees-C. Also while the growth was optimum at 25-degrees-C gro wth did not occur at 35-degrees-C. In regard to the effect of the reac tion pH value, the activity was optimum at pH 5.5-6.5 and did not occu r at pH 8.0, while growth was good at pH 5.5-8.0. In regard to the rea ction NaCl 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 NaCl and decreased with an increase of the concentration, while the growth was similar to the tr end obtained on the activity of the washed cell suspensions. In regard to the reaction histidine concentration, activity increased quantitat ively in the concentration above 100 mug/ml and did not vary in that u nder 10 mug/ml. 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 pre sence of glucose in the growth medium, the activity increased in the p resence of glucose and the activities with incubation time were differ ent between the presence and the absence of glucose, while the pH valu e of the culture decreased with an increase of the activity. In regard to the oxygen tension of the culture medium, the activities were high er in anaerobic culture than in aerobic one, while growth was higher i n the aerobic one.