• Food Science and Biotechnology
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• v.17 no.2
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• pp.219-227
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• 2008

Bacillus thuringiensis was isolated as a pathogen of the sotto disease of silkmoth larvae about a hundred years ago. Since then, this bacterium has attracted attentions of not only insect pathologists but also many other scientists who are interested in its strong and specific insecticidal activity. This has led to the recent worldwide development of B. thuringiensis-based microbial insecticides and insect-resistant transgenic plants, as well as a landmark discovery of par asp orin, a cancer cell-specific cytotoxin produced by B. thuringiensis. In this review, we describe examination of interaction between inclusion proteins of B. thuringiensis and brush border membrane of insects using a surface plasmon resonance-based biosensor, identification and characterization of parasporin-4, the latest parasporin produced by the B. thuringiensis A1470 strain, and an effective method for preparing the parasporin-4 from inclusion bodies expressed in the recombinant Escherichia coli cells.

• The Korean Journal of Zoology
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• v.20 no.1
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• pp.19-28
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• 1977

In order to evaluate the mutagenic potential in animal for these pesticides which were proved to be mutagenic in the bacterial screening system with a metabolic activation in vitro, we have studied in vivo cytogenetic effects on mouse bone marrow by means of the micronucleus test. The clastogenic activity of the chemical is evaluated as the frequency of micronuclei in polychromatic erythrocytes. We have tested six pesticides, insecticides, DDVP and trichlorfon, fungicide, TMTD, herbicides, NIP and MO and growth regula색, maleic hydrazide. It was found that among the tested pesticides only TMTD exhibited minimal activity in inducing micronuclei. Organophosphorus insecticide DDVP that is the most broadly used and economically important chemical, did not increase the micronuclei frequencies in mouse bone marrow cells as with the all other pesticides tested.

• Journal of Microbiology and Biotechnology
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• v.16 no.8
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• pp.1306-1310
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• 2006

Sphingomonas sp. strain SB5 could degrade carbofuran and carbofuran-7-phenol to a hydrolytic product, 2-hydroxy-3-(3-methlypropan-2-o1)phenol, and several red metabolites. However, the chemical structures of the red metabolites have largely remained unidentified. In this study, we identified the structure of one of the red metabolites as 5-(2-hydroxy-2-methyl-propyl)-2,2-dimethyl- 2,3-dihydro-naphtho[2,3-6]furan-4,6,7,9-tetrone by using mass spectrometric and NMR ($^1$H, $^{13}$C) analyses. It is suggested that the red metabolite resulted from condensation of some metabolites in the degradation of 2-hydroxy-3-(3-methlypropan-2-o1)phenol, a hydrolytic product derived from carbofuran. To our knowledge, this is the first paper to report a red metabolite in bacterial degradation of the insecticide carbofuran.

• Korean Journal of Microbiology
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• v.35 no.1
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• pp.61-64
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• 1999

Organophosphorus inseclicide phosphamidon-degrading bacteria were isolated from agricultural soils and identified using Biolog microtiter assay. All Gram-positive degrading bacterial strains belong to genus Bacillus and many Gram-negative bacteria were rare soil species. Among them fast growing strains on phosphamidon-containing minimal medium were sclected and their biodegrading capability wcre measured. YD-17 which was identified as Capnocytophaga gingivalis showed the highest biodegradation rate. It could incrcase the removal of phosphamidon up to 52%. During the biodegradation continuous increase of amount of cell protein was observed, which indicated that phosphamidon was utilized as a carbon source for phosphamidon-degrading bacteria.

• Research in Plant Disease
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• v.26 no.1
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• pp.8-18
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• 2020

Red pepper, one of the major economic crops in Korea, is being affected by anthracnose disease caused by Colletotrichum acutatum. To control this disease, an antagonistic bacterial strain, Bacillus subtilis YGB36 identified by 16S rDNA sequencing, physiological and biochemical analyses is used as a biological control agent. In vitro screening revealed that the strain YGB36 possess strong antifungal activity against the pathogen Cylindrocarpon destructans. The strain exhibited cellulase, protease, amylase, siderophore production and phosphate solubility. In vitro conidial germination of C. acutatum was most drastically inhibited by YGB36 cell suspensions (10⁶ cfu/ml) or culture filtrate. Development of anthracnose symptoms was reduced on detached immature green pepper fruits by treatment with cell suspensions, and its control value was recorded as 65.7%. The YGB36 bacterial suspension treatment enhanced the germination rate of red pepper seeds and promoted root development and growth under greenhouse conditions. The in vitro screening of fungicide and insecticide sensitivity test against YGB36 revealed that the bacterial growth was not affected by any of the insecticides, and 11 fungicides out of 21 used. Collectively, our results clearly suggest that the strain YGB36 is considered as one of the potential biocontrol agents against anthracnose disease in red pepper.

• Journal of Microbiology and Biotechnology
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• v.17 no.10
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• pp.1700-1703
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• 2007

Microorganisms capable of degrading crude oil were isolated and grown in soybean oil as a sole carbon source. The microbial cultures were used to control green peach aphids in vitro. Approximately 60% mortality of aphids was observed when the cultures were applied alone onto aphids. To examine the cultures as a pesticide formulation mixture, the cultures were combined with a low dose of the insecticide imidacloprid (one-fourth dose of recommended field-application rate) and applied onto aphids. The cultures enhanced significantly the insecticidal effectiveness of imidacloprid, which was higher than imidacloprid alone applied at the low dose. The isolated microorganisms exhibited high emulsifying index values and decreased surface tension values after being grown in soybean oil media. GC/MS analyses showed that microorganisms degraded soybean oil to fatty acids. The cultures were suggested to play the roles of wetting, spreading, and sticking agents to improve the effectiveness of imidacloprid. This is the first report on the control of aphids by using oil-degrading microbial cultures.

• Korean Journal of Soil Science and Fertilizer
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• v.18 no.2
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• pp.221-226
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• 1985

This investigation was undertaken to clarify the effects of consecutive application of insecticide (Hexachlorocyclohexane: HCH, 10 ppm each year) and fungicide (Tetrachloroisophthalonitrile: TPN, 40 ppm each year) on changes of the composition of soil bacterial flora in the experimental plots treated with each pesticide for two years. For these purposes, the isolating of bacterial cells growing on albumin agar plate was carried out with non-treated, HCH-treated and TPN-treated soil. And these isolated strains were grouping in accordance with the first diagnostic table of Cowan & Steel based on the morphological and physiological characteristics of bacterial cells. The mortality rate of bacteria was 30% in control, 44% in HCH and 51% in TPN plot respectively, in the process of obtaining pure culture. This suggests that the application of HCH or TPN enriched the fastidious bacteria in soil. The proportion of Gram-negative strains to the total isolates was 37% in control, 37% in HCH and 75% in TPN plot respectively. This means that the application of TPN enriched Gram-negative strains in soil. And the application of TPN increased the number of Gram-negative, nonspore-forming strains, and meanwhile decreased the number of spore-forming strains. In the results, the application of HCH or TPN changed considerably the composition of soil bacterial flora. And the influences of HCH and TPH on changes of the composition of soil bacterial flora were not equal each to each.

• KSBB Journal
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• v.15 no.3
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• pp.219-225
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• 2000

Both the production of high spore concentration and high insecticidal activity are required in the production of Bacillus thuringiensis to be used for the bacterial insecticide. In the production of high cell and spore concentrations of B. thuringiensis the continuous fed-batch culture(CFBC) and intermittent fed-batch culture(IFBC) were investigated at $28^{\circ}C$ by maintaining 40% dissolved oxygen concentration. When the final glucose concentration was 50 g/L the maximum viable cell number obtained using the CFBC with linear gradient feeding was $9.37{\times}109$ cells/mL and maximum spore concentration was $8.33{\times}109$ spores/mL which was approximately 84.4% yield of spore formation. When the final glucose concentration was 100 g/L the aximum viable cell and spore concentrations obtained using the IFBC with pH-statb were $1.38{\times}$1010 cells/mL and $1.35{\times}1010$ spores/mL respectively and the yield of spore formation was approximately 97.8%.

• KSBB Journal
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• v.13 no.6
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• pp.644-648
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• 1998

In the production of a low cost bacterial insecticide, it is important to produce a high spore concentration using low price substrates. Experiments were carried out to investigate the effects of the addition of mineral salts and glucose, and of dissolved oxygen concentration on the cell growth and spore formation of Bacillus thuringiensis var aizawai using a cheap wheat and soybean meal in the batch culture. The maximum viable cell number was 1.2${\times}$109 CFU/mL at 12 hr culture and spore yield was 54.2% at 74 hr culture using an industrial medium containing 20 g/L wheat meal and 30 g/L soybean meal under 1.0 vvm aeration and 200 rpm agitation. The cell growth and the spore formation were not enhanced by the addition of mineral salts in industrial medium, whereas th addition of 10g/L glucose decreased the cell growth and spore formation. We could obtain a maximum viable cell number of 2.2${\times}$109 CFU/mL and spore number of 1.9${\times}$109 CFU/mL at the dissolved oxygen concentration of 60% of saturation. The spore concentration was enhanced approximately by 2 times as compared to the dissolved oxygen concentration of 50%. In the bench-scale culture, the maximum viable cell and spore number were 2.5${\times}$109 CFU/mL, and 2.2${\times}$109 CFU/mL, respectively under 1.0 vvm aeration and 400 rpm agitation. The spore yield was 88% based on the maximum viable cell number. As a result, it was confirmed that the production of high spore concentration could be obtained by a bench-scale culture using an industrial medium.

• Korean journal of applied entomology
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• v.52 no.2
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• pp.115-123
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• 2013

A microbial insecticide "Bt-Plus" has been developed to enhance an insecticidal efficacy of an entomopathogenic bacterium, Bacillus thuringiensis (Bt). However, its wettable powder formulation is not preferred by farmers and industry producers due to relatively high cost. This study aimed to develop a soluble concentrate formulation of Bt-Plus. To this end, an optimal mixture ratio of two bacterial culture broths was determined to be 5:4 (v/v) of Bt and Xenorhabdus nematophila (Xn) along with 10% ethanol preservative. In addition, Bt broth was concentrated by 10 times to apply the mixture at 1,000 times fold dilution. The resulting liquid formulation was sprayed on cabbage crop field infested by late instar larvae of the diamondback moth, Plutella xylostella. The field assay showed about 77% control efficacy at 7 days after treatment, which was comparable to those of current commercial biopesticides targeting P. xylostella. For storage test in both low and room temperatures, the liquid formation showed a relatively stable control efficacy at least for a month. To develop a quality control technique to exhibit a stable control efficacy of Bt-Plus, Bt spore density ($5{\times}10^{11}$ spores/mL) and eight active component concentrations of Xn bacterial metabolites in the formulation products have been proposed in this study.