• Microbiology and Biotechnology Letters
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• v.30 no.3
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• pp.216-222
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• 2002

To Produce the modified Cheongiu that has high ethanol content, an ethanol-tolerant strain Saccharo-myces cerevislae SE2l1 was screened from Saccharomyces cerevisiae Kyokai No. 10 strain. The isolate showed faster growth than in the medium containing 10% ethanol compared with original strain. The isolate produced a higher concentration of ethanol and showed higher resistance to ethanol, high osmolarity and heat than the original strain. The analyses of yeast membrane components indicated that there were no significant changes in composition of sterols and phospholipids between the isolated and the original strain. However, during the fermentation, the iso-lated strain could change the fatty acid composition in the membrane more rapidly in the direction of decreasing membrane unsaturation and accumulate more trehalose in the cell than the original strain. These data suggest that the ability to change its membrane fatty acid composition and to accumulate trehalose may make the isolated strain easily adapt to changes in external condition.

• Microbiology and Biotechnology Letters
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• v.39 no.2
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• pp.104-110
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• 2011

Actinomycetes, Gram positive soil bacteria, are valuable microorganisms which produce useful secondary metabolites including antibiotics, antiparasitic substances, anti-cancer drugs, and immunosuppressants. Although a major family of actinomycetes, known as streptomycetes, has been intensively investigated at the molecular level for several decades, a potentially valuable and only recently isolated non-streptomycetes rare actinomycetes (NSRA) family has been poorly characterized due to lack of proper genetic manipulation systems. Here we report that a PCR-based genome screening strategy was performed with approximately 180 independently isolated actinomycetes strains to isolate potentially valuable NSRA strains. Thanks to this simple PCR-based genome screening strategy we were able to identify only seven NSRA strains, followed by 16S rRNA sequencing for confirmation. Through further bioassays, one potentially valuable NSRA strain (tentatively named Nocardiopsis species MMBL010) was identified which possessed both antifungal and antibacterial activities, along with the presence of polyketide synthase and non-ribosomal peptide synthase genes. Moreover, Nocardiopsis species MMBL010, which was intrinsically recalcitrant to genetic manipulation, was successfully transformed via E. coli-driven conjugation. These results suggest that PCR-based genome screening, followed by the establishment of an E. coli-driven conjugation system, is an efficient strategy to maximize potentially valuable compounds and their biosynthetic genes from NSRA strains isolated from various environments.

• Journal of Microbiology and Biotechnology
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• v.29 no.12
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• pp.1982-1992
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• 2019

The alkaliphilic, calcium carbonate precipitating Bacillus sp. strain AK13 can be utilized in concrete for self-repairing. A statistical experimental design was used to develop an economical medium for its mass cultivation and sporulation. Two types of screening experiment were first conducted to identify substrates that promote the growth of the AK13 strain: the first followed a one-factor-at-a-time factorial design and the second a two-level full factorial design. Based on these screening experiments, barley malt powder and mixed grain powder were identified as the substrates that most effectively promoted the growth of the AK13 strain from a range of 21 agricultural products and by-products. A quadratic statistical model was then constructed using a central composite design and the concentration of the two substrates was optimized. The estimated growth and sporulation of Bacillus sp. strain AK13 in the proposed medium were 3.08 ± 0.38 × 10⁸ and 1.25 ± 0.12 × 10⁸ CFU/ml, respectively, which meant that the proposed low-cost medium was approximately 45 times more effective than the commercial medium in terms of the number of cultivatable bacteria per unit price. The spores were then powdered via a spray-drying process to produce a spore powder with a spore count of 2.0 ± 0.7 × 10⁹ CFU/g. The AK13 spore powder was mixed with cement paste, yeast extract, calcium lactate, and water. The yeast extract and calcium lactate generated the highest CFU/ml for AK13 at a 0.4:0.4 ratio compared to 0.4:0.25 (the original ratio of the B4 medium) and 0.4:0.8. Twenty-eight days after the spores were mixed into the mortar, the number of vegetative cells and spores of the AK13 strain had reached 10⁶ CFU/g within the mortar. Cracks in the mortar under 0.29 mm were healed in 14 days. Calcium carbonate precipitation was observed on the crack surface. The mortar containing the spore powder was thus concluded to be effective in terms of healing micro-cracks.

• Microbiology and Biotechnology Letters
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• v.4 no.3
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• pp.105-110
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• 1976

In the studies of microbiological utilization of cellulosic wastes, cellulolytic fungi were isolated and screened out. At the first stage, 221 cellulolytic fungi were isolated from different sources such as soils, humus, composts and rotten wood debris by enrichment culture techniques. In the second stage, 36 strains of fungi out of those previously isolated were selected for their cellulase activities estimated by means of filter paper degradation, carboxy methyl cellulose liquefaction and cup method. Activities of C$_1$-cellulase, C$\sub$x/-cellulase and filter paper activity were adopted on the final screening stage and five different strains which are tentatively identified as Aspergillus sp.(strain No. AS-9), Penicillium sp. (strain No. KNI-1-2), Trichoderma, sp. (strain No. KI-7-2, KI-7-5, KI-4-1-1B) were selected for their high potency of C$_1$ and C$\sub$x/-cellulase activities. When rice straw milled and treated with NH$_4$OH was hydrolyzed with the crude enzyme Prepared from the culture broth of Trichoderma sp. (strain No. KI-4-1-1B), saccharification rate was obtained up to 26％.

• The Journal of Korean Society of Virology
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• v.29 no.3
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• pp.165-174
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• 1999

To investigate viral pathogenesis and in vivo efficacy of acyclovir (ACV) in mouse HSV-1 encephalitis models, female BALB/c mice aged 5 weeks were inoculated with strain F either intranasally (IN) or intracerebrally (IC). ACV-treatment by intraperitomeal injection with 0, 5, 10 and 25 mg/kg b.i.d. for 6 days was commenced 1 h after infection. Body weight and signs of clinical disease were noted daily up to 2 weeks. $ED_{50}$ of ACV in IN infection was <5 mg/kg and 14.1 mg/kg in IC infection. Tissues of central nervous system were collected from 2 mice per group everyday up to 5 day p.i. and the virus titers were measured. In IN infection model, high titers in eyes and trigeminal nerves were observed. ACV-treatment showed significant reduction of the titers in all the isolated. In IC infection model, cerebrum, cerebellum and brain stem showed high virus titers. ACV-treatment showed less significant reduction of virus titers than that in IN infection model. Reactivation of explanted trigeminal nerves from mice 30 day p.i. was monitored. In all of ACV treated mice reactivation was observed, i.e. even the highest dose of ACV did not inhibit the establishment of viral latency.

• Journal of Microbiology and Biotechnology
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• v.33 no.3
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• pp.329-338
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• 2023

Enterohemorrhagic Escherichia coli (EHEC) is a foodborne pathogen that produces attaching and effacing lesions on the large intestine and causes hemorrhagic colitis. It is primarily transmitted through the consumption of contaminated meat or fresh produce. Similar to other bacterial pathogens, antibiotic resistance is of concern for EHEC. Furthermore, since the production of Shiga toxin by this pathogen is enhanced after antibiotic treatment, alternative agents that control EHEC are necessary. This study aimed to discover alternative treatments that target virulence factors and reduce EHEC toxicity. The locus of enterocyte effacement (LEE) is essential for EHEC attachment to host cells and virulence, and most of the LEE genes are positively regulated by the transcriptional regulator, Ler. GrlA protein, a transcriptional activator of ler, is thus a potential target for virulence inhibitors of EHEC. To identify the GrlA inhibitors, an in vivo high-throughput screening (HTS) system consisting of a GrlA-expressing plasmid and a reporter plasmid was constructed. Since the reporter luminescence gene was fused to the ler promoter, the bioluminescence would decrease if inhibitors affected the GrlA. By screening 8,201 compounds from the Korea Chemical Bank, we identified a novel GrlA inhibitor named Grlactin [3-[(2,4-dichlorophenoxy)methyl]-4-(3-methylbut-2-en-1-yl)-4,5-dihydro-1,2,4-oxadiazol-5-one], which suppresses the expression of LEE genes. Grlactin significantly diminished the adhesion of EHEC strain EDL933 to human epithelial cells without inhibiting bacterial growth. These findings suggest that the developed screening system was effective at identifying GrlA inhibitors, and Grlactin has potential for use as a novel anti-adhesion agent for EHEC while reducing the incidence of resistance.

• Korean Journal of Environmental Biology
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• v.36 no.2
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• pp.190-198
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• 2018

The petroleum industry is an important part of the world economy. However, the massive exposure of petroleum in nature is a major cause of environmental pollution. Therefore, the microbial mediated biodegradation of petroleum residues is an emerging scientific approach used to resolve these problem. Through the screening of diesel contaminated soil we isolated a rapid phenanthrene and a diesel degrading bacterium identified as Enterobacter cancerogenus DA1 strain through 16S rRNA gene sequence analysis. The strain was registered in NCBI with an accession number MG270576. The optimal growth condition of the DA1 strain was determined at pH 8 and $35^{\circ}C$, and the highest degradation rate of the diesel was achieved at this condition. At the optimal condition, growth of the strain on the medium containing 0.05% phenanthrene and 0.1% of diesel-fuel was highest at 45 h and 60 h respectively after the incubation period. Biofilm formation was found significantly higher at $35^{\circ}C$ as compared to $30^{\circ}C$ and $40^{\circ}C$. Likewise, the lipase activity was found significantly higher at 48 h after the incubation compared to 24 h and 72 h. These results suggest that the Enterobacter cancerogenus DA1 could be an efficient candidate, for application through ecofriendly scientific approach, for the biodegradation of petroleum products like diesel.

• Korean Journal of Food Science and Technology
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• v.30 no.3
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• pp.655-659
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• 1998

Bacterial strain showing the strong fibrinolytic activity (2.04 plasmin unit) was screened from Jeot-Gal, Korean salt-fermented fish collected from various region. For the identification, when the strain was characterized morphologically, culturally, and biochemically, it was identified to Bacillus pumilus. And, when the fatty acids composition of the strain was analyzed, it was identified to Bacillus atropheus. Finally, the 16S rRNA partial sequence (V3 region) showed that the fibrinolytic stain screened from Jeot-Gal was identified as Bacillus subtilis. So, we named it Bacillus subtilis KJ-48.

• KSBB Journal
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• v.16 no.4
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• pp.370-375
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• 2001

For the production of new exo-biopolymers from microorganisms, an exe-biopolymer producing bacterial strain was isolated from the composter used in composting of organic wastes. Bacteriological properties of this strain and physicochemical properties of producing exo-biopolymer were investigated. The isolated strain was identified as Enterobacter sp. through its morphological, cultural and physiological characteristics. The results of color reactions, CPC (cetyl pyridinium chloride) precipitation and infra red absorption spectral analysis indicated that this exo-biopolymer was presumed as an acidic polysaccharide with uronic acid. This polysaccharide was identified as hetero-polysaccharide consisting of galactose, mannose and galacturonic acid by gas chromatography, and the molecular weight of exopolysaccharide purified by gel chromatography were about 370,000 daltons. The polysaccharide solutions(0.50-2.0%, w/v) exhibited non-Newtonian flow behavior with pseudoplastic property and showed the ability of gel formation at above 1.5% (w/v) of polysaccharide concentration.

• Korean Journal of Veterinary Research
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• v.33 no.1
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• pp.53-60
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• 1993

Anaerobic bacteria are suggested to be potential source for new antibiotics. In order to search for antibiotics from domestic origin, we collected 800 soil samples across Korean locations and could isolate as many as 989 anaerobic strains. Among them 10, strains were found to have good producing capacity of antibiotics. An anaerobe was finally selected due to secreting antibiotics having high antimicrobial activity towards multiple resistant microorganism(E coli JM 83) transformed by genetic engineering technique. Its morphological, physiological and biochemical charateristics were investigated, together with antimicrobial spectrum therefrom. On antimicrobial spectrum study, substance secreted from this strain, had no activities to fungus and yeast. The selected strain showed G(+) and coccal shape, on Gram, staining and electron scanning microscopy, respectively. Biochemically this strain utilized glucose, fructose lactose, sucrose, but did not arabinose, cellulose, rhamnose, sorbitol, trehalose, mannitol. Catalase test showed negative property. Optimal growth temperature was $37^{\circ}C$. The results obtained above suggest this strain Streptococcus faecium subspp. and we named it Streptococcus sp. An-21-1.