• Korean Journal of Environmental Agriculture
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• v.15 no.4
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• pp.399-405
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• 1996

In the culture medium, the three antifungal fractions against P. capsici were separated by Sephadex G-25 column chromatography and Silica-gel chromatography. The substance A in white powder and the substance B in sticky oil were isolated by ethyl acetate : acetone mixture(7 : 3), and the substance C in yellow powder was isolated by chloroform : ethyl acetate mixture(95 : 5). The crude extract by ethyl acetate from the culture medium acidified to pH 2 was known to inhibit completely the growth of P. capsici at the level of $50mgkg^{-1}$. The substance A and B were known to be effective above the level of $5mgkg^{-1}$, and the substance C was effective above the level of $1mgkg^{-1}$. However, at the level of $20mgkg^{-1}$, the efficiency was in the order of A>C>B. It is apparent on a pot-experiment scale that the three substances effectively control Phytophthora blight of the red-pepper plant grown in the soil inoculated with P. capsici.

• Journal of Microbiology and Biotechnology
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• v.27 no.7
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• pp.1249-1256
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• 2017

In our search for new sources of bioactive secondary metabolites from Streptomyces sp., the ethyl acetate extracts from endophytic Streptomyces SUK 25 afforded five active diketopiperazine (DKP) compounds. The aim of this study was to characterize the bioactive compounds isolated from endophytic Streptomyces SUK 25 and evaluate their bioactivity against multiple drug resistance (MDR) bacteria such as Enterococcus raffinosus, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa, and Enterobacter spp., and their cytotoxic activities against the human hepatoma (HepaRG) cell line. The production of secondary metabolites by this strain was optimized through Thornton's medium. Isolation, purification, and identification of the bioactive compounds were carried out using high-performance liquid chromatography, high-resolution mass liquid chromatography-mass spectrometry, Fourier transform infrared spectroscopy, and nuclear magnetic resonance, and cryopreserved HepaRG cells were selected to test the cytotoxicity. The results showed that endophytic Streptomyces SUK 25 produces four active DKP compounds and an acetamide derivative, which were elucidated as $cyclo-({\text\tiny{L}}-Val-{\text\tiny{L}}-Pro)$, $cyclo-({\text\tiny{L}}-Leu-{\text\tiny{L}}-Pro)$, $cyclo-({\text\tiny{L}}-Phe-{\text\tiny{L}}-Pro)$, $cyclo-({\text\tiny{L}}-Val-{\text\tiny{L}}-Phe)$, and N-(7-hydroxy-6-methyl-octyl)-acetamide. These active compounds exhibited activity against methicillin-resistant S. aureus ATCC 43300 and Enterococcus raffinosus, with low toxicity against human hepatoma HepaRG cells. Endophytic Streptomyces SUK 25 has the ability to produce DKP derivatives biologically active against some MDR bacteria with relatively low toxicity against HepaRG cells line.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.1
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• pp.35-41
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• 2006

Antibacterial activities of the trace elements in combination with the food additives were measured against 6 kinds of food-borne microorganisms such as Escherichia coli, Vibrio parahaemolyticus, Staphylococcus aureus, Bacillus cereus, Bacillus subtilis and Pseudomonas fluorescens. The difference of antibacterial activity was not shown among the kinds of food additives, such as dextrin, gelatin and collagen. Zn and Ge in combination with food additives had strong antibacterial effect. Especially, $1\%$ zinc acetate in combination with $1\%$ gelatin was more effective against P. fluorescens and S. aureus than against Bacillus sp., E. coli and V. parahaemolyticus. Minimum inhibitory concentration of zinc acetate in combination with $1\%$ gelatin appeared to be 0.5 mg/mL on S. aureus and P. fluorescens, and 1.0 mg/mL on E. coli, V. parahaemolyticus, B. cereus and B. subtilis. Minimum bactericidal concentration of zinc acetate in combination with $1\%$ gelatin appeared to be 0.5 mg/mL on P. fluorescens and 1.0 mg/mL on E. coli, V. parahaemolyticus, S. aureus, B. cereus and B. subtilis. The zinc acetate in combination with gelatin showed stronger inhibitory effect in acidic range below pH 6.0, and remained active even after heat treatment at $121^{\circ}C$ for 15 min. In comparison with control, the viable cell counts of fish pastes, which were coated with the solution containing both $1\%$ zinc acetate and $3\%$ gelatin, were decreased by more than 100-fold until the storage of 7 days at $10^{\circ}C$. The results indicate that the combined use of zinc acetate and some food additives could prolong the shelf life of fish pastes by 8 days or more at $10^{\circ}C$.