Abstract
Among 16 different enzymes measured by fluorogenic assay, the arylamidase activity of Salmonella was the highest at pH 7.5. The arylamidase activities of raw foods were, however, about five-times higher than that of Salmonella at pH 7.5. Six different arylamidases were examined for their optimal pH values; the alanine-arylamidase activity of Salmonella was higher than those of raw pork, raw chicken, and raw beef at pH 9 and pH 10. Dulcitol-malachite green-novobiocin (DMN) medium containing 0.01% malachite green and 1μg/ml novobiocin was effective for enrichment of Salmonella. In the presence of 5mM EDTA, the alanine-arylamidase activity increased to by 3.8 times that measured without EDTA. Although E. aerogenes grew and exibited a high alanine-arylamidase activity at an initial cell number of 3×103, 1-10 cells of Salmonella were detected by measuring the enzyme activity after cultivation in DMN medium at 30°C for 22 hr with shaking. The activity increased by increasing the initial cell number of Salmonella.
