• Journal of Dairy Science and Biotechnology
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• 제39권3호
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• pp.121-127
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• 2021

Yogurt is produced by bacterial fermentation of milk and contains lactic acid bacteria (LAB), which produce various metabolites such as organic acid, hydrogen peroxide, and bacteriocin. This study aimed to investigate cell-free supernatants (CFS) of LAB isolated from Tibetan yogurt. CFS (TY1, TY2, TY3, TY4, TY5, TY6, and TY7) from selected strains of LAB were co-incubated with four different foodborne pathogenic bacteria, namely E. coli O157:H7, Listeria monocytogenes, Salmonella typhimurium, and Staphylococcus aureus. Inhibition of foodborne pathogenic bacterial growth was not affected in the presence of CFS (pH 6.5). In contrast, CFS without neutralization completely inhibited the growth of the bacteria. Furthermore, when the concentration of CFS (without neutralization) was changed to 1:4 and 1:8, a difference in inhibition was observed between Gram-positive and Gram-negative bacteria. CFS more effectively inhibited the growth of Gram-negative E. coli O157:H7 and S. Typhimurium than Gram-positive L. monocytogenes and S. aureus. These results suggest that organic acids in LAB may inhibit the growth of foodborne pathogenic bacteria, particularly Gram-negative bacteria.

• 한국미생물·생명공학회지
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• 제50권2호
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• pp.255-269
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• 2022

Actinomycetes isolated from marine habitats represent a promising source of bioactive substances. Here, we report on the isolation, identification, productivity enhancement and application of the bioactive compounds of Streptomyces qinglanensis H4. Eighteen marine actinomycetes were isolated and tested for resistance to seven bacterial diseases. Using 16S rRNA sequencing analysis (GenBank accession number MW563772), the most powerful isolate was identified as S. qinglanensis. Although the strain produced active compound(s) against a number of Gram-negative and Gram-positive bacteria, it failed to inhibit pathogenic fungi. The obtained inhibition zones were 22.0 ± 1.5, 20.0 ± 1, 16.0 ± 1, 12.0 ± 1, 22.0 ± 1 and 24.0 ± 1 mm against Bacillus subtilis ATCC 6633, Escherichia coli ATCC 19404, Enterococcus faecalis ATCC 29212, Pseudomonas aeruginosa ATCC 9027, Candida albicans ATCC 10231 and Staphylococcus aureus ATCC6538, respectively. To maximize bioactive compound synthesis, the Plackett-Burman design was used. The productivity increased up to 0.93-fold, when S. qinglanensis was grown in optimized medium composed of: (g/l) starch 30; KNO₃ 0.5; K₂HPO₄ 0.25; MgSO₄ 0.25; FeSO₄·7H₂O, 0.01; sea water concentration (%) 100; pH 8.0, and an incubation period of 9 days. Moreover, the anticancer activity of S. qinglanensis was tested against two different cell lines: HepG2 and CACO. The inhibition activities were 42.96 and 57.14%, respectively. Our findings suggest that the marine S. qinglanensis strain, which grows well on tailored medium, might be a source of bioactive substances for healthcare companies.

• 식물병연구
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• 제29권2호
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• pp.174-183
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• 2023

관행적 화학농약의 식물병 관리 및 치료의 한계적인 효과는 유익한 세균이나 미생물을 이용한 식물병 제어 방법 개발의 필요성을 나타낸다. 지속 가능한 농업은 특히 다양한 항생물질과 이차 대사 생성물을 생산하는 방선균의 농업적 중요성을 시사하며, Streptomyces globiosporus SP6C4균주와 Streptomyces sp. S8은 강력한 항균 작용을 가지고 있으며, 지속가능한 농업에서 작물 생장을 개선하기 위한 우수한 균주로 인정되고 있다. 본 연구에서는 다양한 질소원과 탄소원을 활용하여 대상 미생물 Streptomyces 두 균주의 생장을 촉진시키는 방법을 조사하였다. L-글루타민과 L-시스테인이 첨가된 조건에서 S. globiosporus SP6C4와 Streptomyces sp. S8 균주의 포자 생성 능력이 증가하였으며, 각 균주의 생장이 촉진되었다. 이러한 결과는 유용 미생물의 대량배양 기술의 범위 확장과 농업미생물의 실용화에 기여할 것으로 생각된다.

• 한국응용곤충학회지
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• 제51권1호
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• pp.47-58
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• 2012

신작물보호제로 개발된 '비티플러스'의 천적에 대한 영향평가가 이뤄졌다. 분석된 천적은 두 종의 기생성 천적인 콜레마니진디벌($Aphidius$ $colemani$) 및 황온좀벌($Eretmocerus$ $eremicus$)과 네 종의 포식성 천적인 무당벌레($Harmonia$ $axyridis$), 애꽃노린재($Orius$ $laevigatus$), 지중해이리 응애($Amblyseius$ $swirskii$) 및 칠레이리응애($Phytoseiulus$ $persimilis$)를 포함했다. '비티플러스'는 세 가지 곤충병원세균($Xenorhabdus$ $nematophila$(Xn), $Photorhabdus$ $temperata$ subsp. $temperata$(Ptt), $Bacillus$ $thuringiensis$(Bt))과 세균 대사물질(BM)을 조합하여 개발되었다. 배추좀나방($Plutella$ $xylostella$) 4령충에 대해서 세 종류의 '비티플러스'('Xn+Bt', 'Ptt+Bt' 그리고 'BM+Bt') 모두는 Bt 단독에 비해 높은 살충력을 나타냈다. '비티플러스'의 천적에 대한 영향에서 세균배양액 혼합체('Xn+Bt' 또는 'Ptt+Bt')는 접촉독성 및 섭식독성 분석에서 모두 독성이 낮은 것으로 나타났다. 그러나 'BM+Bt'는 일부 독성을 보였으며, 특별히 지중해이리응애와 칠레이리응애에 대해서 높은 독성을 나타냈다. 이들 세균대사물질의 살비효과를 점박이응애($Tetranychus$ $urticae$)를 대상으로 분석하였다. 각 대사물질별로 상이한 살비력을 보인 가운데, '비티플러스'에 이용된 대사물질 복합체는 반수치사약량이 218.7 ppm(95% 신뢰구간: 163.2 - 262.3)으로 비교적 높은 살비효과를 나타냈다. 이들 물질의 독성은 Sf9 세포주에 대한 세포독성 분석을 통해 나타났다. 특별히 'BM+Bt' 제조에 사용된 주성분인 벤질리덴아세톤은 낮은 농도에서도 높은 세포독성을 보였다.

• Journal of Applied Biological Chemistry
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• 제51권6호
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• pp.253-261
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• 2008

Isoflavone daidzein is a phytoestrogen widely distributed in Leguminosae and is especially rich in the soybean. The C6-C3 (rings B and C) unit of isoflavones is derived from the phenylpropanoid pathway and the remaining C6 (ring A) unit is from the polyketide pathway. This unique carbon skeleton is the result of isomerization of the flavone catalyzed by the isoflavone synthase, a cytochrome P450 enzyme. The isoflavones daidzein and genistein are present in the plant mostly in the glucosylated forms. However, in the human intestine, the glycosidic linkage is broken, and the free form is uptaked into blood stream. The free form is further metabolized into various reduction products to end up at the equol, which is known to have the most potent estrogenic effect among the metabolites. Several human intestinal bacteria that can convert daidzein into equol have been described, and the study into the chemistry and biochemistry of the daizein reduction would be rewarding to the improvement of the human health.

• Journal of Microbiology and Biotechnology
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• 제26권3호
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• pp.488-492
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• 2016

Rhodococcus species have become increasingly important owing to their ability to degrade a wide range of toxic chemicals and produce bioactive compounds. Here, we report isolation of the Rhodococcus sp. KB6, which is a new leaf-inhabiting endophytic bacterium that suppresses black rot disease in sweet potato leaves. We determined the 7.0 Mb draft genome sequence of KB6 and have predicted 19 biosynthetic gene clusters for secondary metabolites, including heterobactins, which are a new class of siderophores. Notably, we showed the first internal colonization of host plants with Rhodococcus sp. KB6 and discuss its potential as a biocontrol agent for sustainable agriculture.

• Fisheries and Aquatic Sciences
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• 제17권2호
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• pp.215-222
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• 2014

To explore marine microorganisms with medical potential, we isolated and identified marine bacteria from floats, marine algae, animals, and sponges collected from Jeju Island, Korea. We isolated and identified 21 different strains from the marine samples by 16S rRNA analysis, cultured them in marine broth, and extracted them with ethyl acetate (EtOAc) to collect secondary metabolite fractions. Next, we evaluated their anti-oxidative and anti-inflammatory effects. Among the 21 strains, the secondary metabolite fraction of Bacillus badius had both strong antioxidant and anti-inflammatory activity, and thus was selected for further experiments. An antioxidant compound detected from the secondary metabolite fraction of B. badius was purified by preparative centrifugal partition chromatography (n-hexane:EtOAc:methanol:water, 4:6:4:6, v/v), and identified as diolmycin A2. Additionally, diolmycin A2 strongly inhibited nitric oxide production. Thus, we successfully identified a significant bioactive compound from B. badius among the bacterial strains collected from Jeju Island.

• 한국환경과학회지
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• 제18권4호
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• pp.435-443
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• 2009

A bacterial strain SY-97 that showed algicidal activity against Cochlodinium polykrikoides was isolated from coastal water of Uljin (eastern coast of Korea) in August, 2005. The isolated strain was identified as Brachybacterium sp. by morphological and biological tests, and analysis of 16S rDNA sequence. The optimal culture conditions for the growth of strain SY-97 were $30^{\circ}C$, initial pH 7.0, and salinity 2.0%. From the result of cell culture insert experiment, Brachybacterium sp. SY-97 is assumed to produce secondary metabolites which have algicidal activity. When 10% culture filtrate of this strain was applied to C. polykrikoides ($1.2{\times}10^4\;cells/m{\ell}$) cultures, 100% of C. polykrikoides cells was destroyed within 15 hours. The released algicides were heat-tolerant to $100^{\circ}C$ and stable in pH $6.0{\sim}10.0$. These results suggest that Brachybacterium sp. SY-97 is potentially useful for controlling outbreaks of C. polykrikoides.

• Journal of Microbiology and Biotechnology
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• 제22권1호
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• pp.13-24
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• 2012

The genetic diversity of plant growth-promoting rhizobacterial (PGPR) fluorescent pseudomonads associated with the sugarcane (Saccharum officinarum L.) rhizosphere was analyzed. Selected isolates were screened for plant growthpromoting properties including production of indole acetic acid, phosphate solubilization, denitrification ability, and production of antifungal metabolites. Furthermore, 16S rDNA sequence analysis was performed to identify and differentiate these isolates. Based on 16S rDNA sequence similarity, the isolates were designated as Pseudomonas plecoglossicida, P. fluorescens, P. libaniensis, and P. aeruginosa. Differentiation of isolates belonging to the same group was achieved through different genomic DNA fingerprinting techniques, including randomly amplified polymorphic DNA (RAPD), amplified ribosomal DNA restriction analysis (ARDRA), repetitive extragenic palindromic (REP), enterobacterial repetitive intergenic consensus (ERIC), and bacterial repetitive BOX elements (BOX) analyses. The genetic diversity observed among the isolates and rep-PCR-generated fingerprinting patterns revealed that PGPR fluorescent pseudomonads are associated with the rhizosphere of sugarcane and that P. plecoglossicida is a dominant species. The knowledge obtained herein regarding the genetic and functional diversity of fluorescent pseudomonads associated with the sugarcane rhizosphere is useful for understanding their ecological role and potential utilization in sustainable agriculture.

• Journal of Microbiology and Biotechnology
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• 제14권4호
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• pp.766-771
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• 2004

Julong 601, a Gram-positive anaerobic bacterium strain capable of cleaving the C-ring of isoflavones daidzein and genistein, was isolated from human feces. BLAST search revealed that its complete 16S rDNA gene sequence has 99% similarity to Eubacterium ramulus. Metabolites of daidzein and genistein were determined as O-desmethylangolensin (O-Dma) and 2-(4-hydroxyphenyl) propionic acid (2-HPPA), respectively, based on UV, EI-MS, and $^1H$ and ^{13}C$ NMR spectral analyses. Enantiomers of O-Dma and 2-HPPA were isolated by chiral stationary-phase HPLC (CSP HPLC). Cleavage of the C-ring of daidzein and genistein by strain Julong 601 was highly enantioselective. Specific rotation ([$\alpha]_D$) and circular dichroism (CD) spectra of the enantiomers are reported here for the first time. Biotransformation kinetics of daidzein and genistein indicated that the C-ring of genistein has a higher susceptibility to bacterial degradation than that of daidzein.