In the course of the studying the microbial degradation of organic compounds in the sea, the degradations of phenol, benzoic acid, o-hydroxybenzoic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, o-cresol, m-cresol and p-cresol in sea water were examined. Degradation mixtures were prepared from sea water, collected in Kure Bay, by addition of each substrate, respectively. Then the mixtures were incubated in the dark at 20°C. Decrease of the substrate was determined on the basis of a quantitative analysis by use of high performance liquid chromatography (HPLC). Judging from the incubation conditions and observations of the degradation mixtures incubated, it was assumed that the microbial degradations of substrates were produced by the bacterial population in sea water. The bacterial population in the mixtures more actively degraded hydroxybenzoic acids and benzoic acid than phenol. To degrade phenol, the bacterial population required an acclimation period of one or two days. However, no or little acclimation was necessary for the degradation of hydroxybenzoic acids and benzoic acid. Cresols were more nondegradable than the other substrates. One or two days acclimation was required for bacterial degradation of cresols, and a considerable proportion of the cresols had not been degraded after 17 days incubation. The degradation curves of cresols showed remarkable differences. It was revealed that degradation of the cresols was influenced by the position of the functional group. On the other hand, no marked difference, arising from their molecular structures, was recognized in the degradation curves of hydroxybenzoic acids.

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A serine protease was purified to homogeniety from the culture supernatant of a marine bacterium, Vibrio anguillarum by a 4-step procedure, ammonium sulfate precipitation, G-100 gel filtration, and two rounds of phenyl-Sepharose chromatography. The molecular weight of the enzyme was estimated to be 30kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration. The enzyme activity was inhibited by diisopropyl fluorophosphate, phenylmethyl sulfonyl fluoride, Leupeptin, and Chymostatin. The optimum temperature was 37°C and the optimum pH of the enzyme was 9.0.Mg²⁺ and Ca²⁺ at 10mM enhanced the enzyme activity by 161 and 124%, and stabilized the activity when exposed between 15 to 42°C. The enzyme hydrolyzed strongly butyloxycarbonyl-leucyl-seryl-threonyl-arginyl-4-methylcoumaryl-7-amide among 17 peptydyl-4-methylcoumaryl-7-amides, indicating narrow substrate specificity. The alkaline serine enzyme shows similar substrate specificity to a known metalloprotease. However, this novel serine protease did not show anticoagulation activity as detected in the metalloprotease, suggesting a different function in this bacterium.

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