• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.4
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• pp.471-476
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• 1998

Microbiological spoilage of marine fish is complex process occurring by bacteria, yeasts and molds. There have been rare study for saprophytic yeasts although having enormous numbers of bacteriological studies on the spoilage of marine fish. The 14 genera of yeasts isolated from mackerel (Scomber japonicus) with high frequency of occurrence were Candida sp., Rhodotorula sp., Torulopsis sp., Cryptotoccus sp. and Tricosporon sp. Among these ones Candida lipolytica was identified as the strongest proteolytic yeast, then named Candida lipolytica FM5 (C. lipolytica FM5). C. lipolytica FM5 showed optimum growth at $25^{\circ}C$, pH 7.0 and could grow at $5^{\circ}C$ and in medium containing $10\%$ sodium chloride, To evaluate the saprophytic activity of the selected strain, C, lipolytica FM5 and Pseudomonas fluorescens ATCC 17571 which is one of representative spoilage bacteria were individually inoculated into the sterilized fish muscle homogenates, and then pH changes and volatile basic nitrogen (VBN) values were checked during the storage at various temperatures. According to the experimental results, the productions of VBN by C. lipolytica FM5 in the fish muscle homogenates were 50 mg-N/100 g at $5^{\circ}C$, 152 mg-N/100 g at $15^{\circ}C$ and 379 mg-N/100 g at $25^{\circ}C$ for 1 week storage, respectively. Above results were nearly same as in case of Ps. fluorescens ATCC 17571 inoculation. It suggest that sapyophytic yeasts also have important role in spoilage of marine fish.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.5
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• pp.631-636
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• 1998

Candida lipolytica(C. lipolytica) FM5 was selected as one of the strong saprophytic yeasts isolated from mackerel (Scomber japonicus). The selected strain could produce extracellular proteolytic enzyme. The effective medium for production of proteolytic enzyme by C. lipolytica FM5 was TPPY broth containing Bacto-tryptone $0.5\%$, proteose peptone $0.5\%$, yeast extract $0.25\%$, NaCl $0.5\%$ and $CaCl_2\;0.2\%$. The pattern of proteolytic enzyme production by C. lipolytica FM5 was the almost same as that of growth curve of the strain. Namely, the enzyme production was begun from the early stage of exponential phase and it was reached the highest at the begining of the stationary phase of the yeast growth. The optimum toeperature of the produced proteolytic enzyme was $35^{\circ}C$ and its activity was not significantly changed by pH between 6.5$\~$9.0 and also it was not significantly affected by several kinds of cations such as $Ca^{2+},\;Cu^{2+},\;Fe^{2+}$ and $Mg^{2+}$ but it was affected negatively by some cations such as $Zn^{2+},\;Mn^{2+}$ and $K^+$.