• Proceedings of the Microbiological Society of Korea Conference
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• 2001.11a
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• pp.46-53
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• 2001

A commensal thermophile, Symbiobacterium toebii, isolated from hay compost (toebii) in Korea commensally interacted with a thermophilic Geobacillus toebii sp. nov., which was a new species within the genus Geobacillus on the basis of the phenotypic traits and molecular systematic data. S. toebii required the crude extracts and/or culture supernatant of the Geobacillus toebii for axenic growth and could grow on the temperature between 45 and $70^{\circ}C$ (optimum: $60^{\circ}C$; 2.4 h doubling time) and pH 6.0 and 9.0 (optimum: pH 7.5). The G+C content of the genomic DNA was $65 mol\%$, and the major quinones were MK-6 and MK-7. A phylogenetic analysis of its 16S rDNA sequence indicated that Symbiobacterium toebii was closely related with solely reported Symbiobacterium thermophilum. The presence of the commensal thermophile 16S rDNA and accumulation of indole in all the enriched cultures indicate that Symbiobacterium toebii is widely distributed in the various soils. The genome of S. toebii constituted a circular chromosome of 3,280,275 base pairs and there was not an extra-chromosomal element (ECE). It contained about 4,107 predicted coding sequences. Of these protein coding genes, about $45.6\%$ was encoded well-known proteins and annotated the functional assignment of 1,874 open reading frames (ORFs), and the rest predicted to have unknown functions. The genes encoding thermostable tyrosine phenol-lyase and tryptophan indole-lyase were cloned from the genomic DNA of S. toebii and the enzymatic production of L-tyrosine and L-tryptophan was carried out with two thermostable enzymes overexpressed in recombinant E. coli.

• Korean Journal of Microbiology
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• v.41 no.4
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• pp.293-299
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• 2005

Many isolates from soil of Korean ginseng rhizosphere did not show remarkable growth on full strength of the conventional nutrient broth (NB medium) but grew on its 100-fold dilution (DNB medium). Six hundred-forty strains were isolated as oligotrophic bacteria. In the course of screening for new bioactive compounds from oligotrophic bacteria from soil, 8 strains which had appeared to form of clear zone on a medium containing colloidal chitin as a sole carbon source were selected for further studies. Strain CR42 hydrolyzed a fluorogenic analogue of chitin, 4-methylumbelliferyl-D-glucosaminide (MUF-NAG) . Mo st of the culture supernatant of these isolates hydrolyzed 4-methylumbelliferyl-D-N,N'-diacetylchitobioside (MUF-diNAG). The isolates were heterogeneous and categorized to gamma- and beta-proteobacteria, Bacillaceae, Actinobactepia, and Bacteroides by 16S rRNA analysis. Two strains, WR164 and CR18, had a 16S rRNA sequence of $95-96\%$ identical to uncultured bacteria. It was observed that CR2 and CR75 could inhibit the growth of Colletotrichum gloeosporioides with hyphal extention-inhibition assay on PDA plate supplemented with $1\%$ colloidal chitin.

• Journal of Microbiology and Biotechnology
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• v.8 no.2
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• pp.101-110
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• 1998

The extent of biological diversity being revealed by molecular techniques accentuates the need to develop methods to isolate and culture the large numbers of microorganisms that remain to be studied. The discovery and characterization of novel microorganisms will provide information useful in understanding microbial ecosystems and have the potential to lead to new products for the biotechnology industry. In this review, the use of innovative techniques and exploration of unusual ecosystems, that have begun to address the challenge of isolating the "uncultured" members of the microbial population, are examined.

• Bulletin of the Korean Chemical Society
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• v.28 no.9
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• pp.1591-1594
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• 2007

• Journal of Microbiology and Biotechnology
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• v.19 no.5
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• pp.495-501
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• 2009

A new spore display method is presented that enables recombinant proteins to be displayed on the surface of Bacillus spores via fusion with InhA, an exosporium component of Bacillus thuringiensis. The green fluorescent protein and $\beta$-galactosidase as model proteins were fused to the C-terminal region of InhA, respectively. The surface expression of the proteins on the spores was confirmed by flow cytometry, confocal laser scanning microscopy, measurement of the enzyme activity, and an immunogold electron microscopy analysis. InhA-mediated anchoring of foreign proteins in the exosporium of Bacillus spores can provide a new method of microbial display, thereby broadening the potential for novel applications of microbial display.

• Food Science and Biotechnology
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• v.15 no.6
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• pp.920-924
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• 2006

The microbiological safety of foodservice facilities and side dishes in 6 elementary schools and 6 universities in the Jeolla-do region was evaluated. The micro-aerosol evaluation of foodservice facilities including the kitchen, refrigerators, and freezers showed a comparatively high level of microbial contamination. In the microbial safety evaluation of cooking utensils and appliances, the total plate counts of serving tables, cutting boards, and food plates were comparatively high, but did not reveal significant counts of coliforms, Staphylococcus aureus, and Escherichia coli were both below the general limit of microbial contamination. The microbiological safety of the cooking utensils and appliances were satisfactory. In the microbiological safety evaluation of side dishes served at these foodservice facilities, microbial counts were generally below the limit of microbial contamination.

• Journal of Marine Bioscience and Biotechnology
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• v.14 no.2
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• pp.112-123
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• 2022

Photosynthetic bacteria (PSB) play an important role in water purification, and their application is beneficial for sustainable aquaculture. However, maintaining the microbial stability of PSB from subculturing to preservation is a challenging task. Since improvement in the microbial stability of PSB is a crucial parameter, optimized conditions for cell immobilization and lyophilization were investigated. In PSB immobilization, 0.1-M CaCl₂ was found to be the most effective divalent metal ion solution in terms of cost-effectiveness, resulting in beads with a 4-mm diameter and high loading (1.91×10⁹ CFU/mL) of viable cells. Maintenance of cell viability, external appearance, and color of PSB beads was best in 3.5% NaCl during storage. In lyophilization, the addition of skim milk (9%) and dextrose (2%) as cryoprotective additives allowed the highest cell viability. Over an 18-week shrimp breeding period, when optimally manufactured beads and lyophilized powder of PSB were applied to shrimp aquaculture water, NH⁴⁺, NO₃^-, and NO₂^- were more effectively removed by 55%, 100%, and 100%, respectively, compared to controls. Thus, microbial stability of PSB through optimized cell immobilization and lyophilization was successfully enhanced, enabling a wide application.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2002.10a
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• pp.88-88
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• 2002

• Journal of Microbiology and Biotechnology
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• v.6 no.2
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• pp.98-102
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• 1996

A thermostable tyrosine phenol-lyase gene of a thermophilic Symbiobacterium species was cloned and overexpressed in Escherichia coli in order to produce the biocatalyst for the synthesis of 3, 4-dihy-droxyphenyl-L-alanine (L-DOPA). The substrates used for the synthetic reaction were pyrocatechol, so-dium pyruvate, and ammonium chloride. The enzyme was stable up to $60^{\circ}C$, and the optimal temperature for the synthesis of L-DOPA was $37^{\circ}C$ . The optimal pH of the reaction was about 8.3. Enzyme activity was highly dependent on the amount of ammonium chloride and the optimal concentration was estimated to be 0.6 M. In the case of pyrocatechol, an inactivation of enzyme activity was observed at con-centrations higher than 0.1 M. Enzyme activity was increased by the presence of ethanol. Under op-timized conditions, L-DOPA production was carried out adding pyrocatechol and sodium pyruvate to the reaction solution intermittently to avoid substrate depletion during the reaction. The concentration of L-DOPA reached 29.8 g/l after 6 h, but the concentration didn t increase further because of the formation of byproducts by a non-enzymatic reaction between L-DOPA and pyruvate.

• Journal of Microbiology and Biotechnology
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• v.25 no.5
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• pp.672-680
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• 2015

As a global regulatory gene in Streptomyces, afsR can activate the biosynthesis of many secondary metabolites. The effect of afsR on the biosynthesis of a phenazine metabolite, lomofungin, was studied in Streptomyces lomondensis S015. There was a 2.5-fold increase of lomofungin production in the afsR-overexpressing strain of S. lomondensis S015 N1 compared with the wild-type strain. Meanwhile, the transcription levels of afsR and two important genes involved in the biosynthesis of lomofungin (i.e., phzC and phzE) were significantly upregulated in S. lomondensis S015 N1. The optimization of metal chlorides was investigated to further increase the production of lomofungin in the afsR-overexpressing strain. The addition of different metal chlorides to S. lomondensis S015 N1 cultivations showed that CaCl₂, FeCl₂, and MnCl₂ led to an increase in lomofungin biosynthesis. The optimum concentrations of these metal chlorides were obtained using response surface methodology. CaCl₂ (0.04 mM), FeCl₂ (0.33 mM), and MnCl₂ (0.38 mM) gave a maximum lomofungin production titer of 318.0 ± 10.7 mg/l, which was a 4.1-fold increase compared with that of S. lomondensis S015 N1 without the addition of a metal chloride. This work demonstrates that the biosynthesis of phenazine metabolites can be induced by afsR. The results also indicate that metal chlorides addition might be a simple and useful strategy for improving the production of other phenazine metabolites in Streptomyces.