Recently, consumer's demand for natural preservatives is increasing because of residual toxicity, mutagenicity and etc. of synthetic preservatives and the study of natural preservatives is being done. In this study, antimicrobial activity of spices was investigated Fungi occurred in bread and a noodle without mustard after 3days and 4days, respectively. However, they didn't occur in bread and noodle with mustard ball. Temperature of the water used in mixing-up mustard powder didn't affect antimicrobial activity of mustard. Fungi occurred in bread with cinnamon, Japanese pepper or horseradish after 4days, 4days or 6days, respectively. However, there wasn't the occurrence of fungi in bread with mustard after 8days, yet. Mustard and horseradish of extracts by water of spices had a strong antimicrobial activity. But the extracts by ethanol had low antimicrobial activity.

V. parahaemolyticus possessed an extracellular alkaline protease activity during the stationary growth phase. Various factors such as initial pH of medium, incubation temperature and shaking rate were investigated for optimizing the production of allcaline protease from V. parahaemolyticus ATCC 17802. Maximal activity of the protease was obtained when the bacteria were grown in 2% skim milk medium in 0.1 M tris/HCl buffer (pH 7.6). Maximal activity of the protease was obtained when the bacteria were grown at initial pH of 7.6, incubation temperature of 37℃ and shaking rate of 250 rpm.

V. parahaemolyticus possessed an extracellular alkaline protease activity during the stationary growth phase. Various factors such as nitrogen sources, the concentration of NaCl and metal ions were investigated for optimizing the production of alkaline protease from V. parahaemolyticus ATCC 17802. Among the nitrogen sources tested skim milk showed the distinct increase of the activity and the activity was the highest at 2% in final concentration after 60 hours incubation. The addition of NaCl and metal ions did not increase the alkaline protease activity. CoC1₂, CuC1₂, and HgCl rather highly inhibited alkaline protease production.

Nine strains of pathogenic Vibrio sp. of clinical and environmental origin were examined for the degradation of gelatin, casein and hemolysin which is important to the virulence of this bacterium. Culture filtrates of all nine strains of Vibrio exhibited proteolytic activities. Especially, four strains of V. parahaemolyticus and one V. alginolyticus showed strong gelatin-degrading activity. In terms of hemolytic activity, three V. parahaemolyticus and V. mimicus showed strong β-hemolysis whereas those of strains of V. alginolyticus, V. fluuialis, V. uulnificus examined lacked this activity.