• Korean journal of applied entomology
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• v.50 no.3
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• pp.171-178
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• 2011

Bacillus thuringiensis (Bt) is a bacterial biopesticide against insect pests, mainly lepidopterans. Spodoptera exigua and Plutella xylostella exhibit significant decreases in Bt susceptibility in late larval instars. To enhance Bt pathogenicity, we used a mixture treatment of Bt and other bacterial metabolites which possessed significant immunosuppressive activities. Mixtures of Bt with culture broths of Xenorhabdus nematophila (Xn) or Photorhabdus temperata ssp. temperata (Ptt) significantly enhanced the Bt pathogenicity against late larval instars. Different ratios of Bt to bacterial culture broth had significant pathogenicities against last instar P. xylostella and S. exigua. Five compounds identified from the bacterial culture broth also enhanced Bt pathogenicity. After determining the optimal ratios, the mixture was applied to cabbage infested by late instar P. xylostella or S. exigua in greenhouse conditions. A mixture of Bt and Xn culture broth killed 100% of both insect pests when it was sprayed twice, while Bt alone killed less than 80% or 60% of P. xylostella and S. exigua, respectively. Other Bt mixtures, including Ptt culture broth or bacterial metabolites, also significantly increased pathogenicity in the semi-field assays. These results demonstrated that the Bt mixtures collectively names "Bt-Plus" can be developed into potent biopesticides to increase the efficacy of Bt.

• Korean journal of applied entomology
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• v.51 no.1
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• pp.39-45
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• 2012

The entomopathogenic bacterium, $Xenorhabdus$ sp., was isolated from an entomopathogenic nematode, $Steinernema$ $monticolum$. When these bacteria were injected into the hemocoel of the diamondback moth, $Plutella$ $xylostella$, they caused significant mortality. However, the bacterium was not pathogenic when it was administered orally. This study showed that $Xenorhabdus$ sp. significantly enhanced oral pathogenicity of $Bacillus$ $thuringiensis$ (Bt) against the last instar larvae of $P.$ $xylostella$. Different ratios of culture broth of $Xenorhabdus$ sp. and Bt showed significantly different pathogenicities against $P.$ $xylostella$. In field tests, the optimal bacterial mixture significantly enhanced control efficacy against $P.$ $xylostella$ compared to Bt treatment alone. These results demonstrated that $Xenorhabdus$ sp. culture broth can be developed as a potent biopesticide by enhancing the insecticidal efficacy of Bt.

• Korean journal of applied entomology
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• v.53 no.3
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• pp.271-280
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• 2014

Some bacterial metabolites of Xenorhabdus nematophila (Xn) inhibit phospholipase $A_2$ ($PLA_2$) activity to shutdown eicosanoid biosynthesis in target insects. However, little has been known about the target insect $PLA_2$ of these bacterial metabolites. Eight bacterial metabolites identified in Xn culture broth exhibited significant insecticidal activities against larvae of both lepidopteran species of Plutella xylostella and Spodoptera exigua. Moreover, these bacterial metabolites significantly enhanced insecticidal activities of Bacillus thuringiensis (Bt). To determine target $PLA_2$, we cloned and over-expressed cellular $PLA_2$ ($SecPLA_2$) of S. exigua. Purified $SecPLA_2$ catalyzed phospholipids derived from the fat body and released several polyunsaturated fatty acids. Most Xn metabolites significantly inhibited $SecPLA_2$ activity, but were different in their inhibitory activities. There was a positive correlation between the inhibition of $SecPLA_2$ and the enhancement of Bt insecticidal activity. These results indicate that $SecPLA_2$ is a molecular target inhibited by Xn metabolite.

• Korean journal of applied entomology
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• v.53 no.3
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• pp.239-246
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• 2014

Two congener species of Grapholita molesta and G. dimorpha have similar host ranges and adult occurrence patterns. In addition, the two species commonly use cis-8-dodecenyl acetate (Z8-12:Ac) and trans-8-dodecenyl acetate (E8-12:Ac) as their major sex pheromone components. The commercial lures made of the two components, therefore, suffer a mixed attraction of these two species. This study was conducted to assess any effect of their known minor sex pheromone components to reduce the mixed attraction. When cis-8-tetradecenyl acetate (Z8-14:Ac) was added to the commercial sex pheromone consisting of Z8-12:Ac/E8-12:Ac = 85/15, the attraction to G. dimorpha was not affected, but its attraction to G. molesta was significantly reduced. However, the addition of either dodecanyl acetate (12:Ac) or tetradedecanyl acetate (14:Ac) did not influence on the attraction of both species to the commercial lure. The addition of E8-14:Ac to 3-component sex pheromone, Z8-12:Ac/E8-12:Ac/Z8-14:Ac = 85/15/10, the attraction to G. dimorpha was rather significantly suppressed. From these results, the 3-component sex pheromone, Z8-12:Ac/E8-12:Ac/Z8-14:Ac = 85/15/10 was suggested as an improved composition of sex pheromone lure for G. dimorpha.

• Korean journal of applied entomology
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• v.42 no.2
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• pp.145-152
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• 2003

Field application of the entomopathogenic nematode, Steinernema carpncapsae, is limited by its susceptibility to UV irradiation and desiccation especially at leaf spray control. This study was conducted to develop the control technique using alginate biocapsulation of the nematodes against the beet armyworm, Spodoprera exigua and the tobacco cutworm, Sp. litura that are normally infesting hosts above ground level. The alginate capsules including infective juveniles gave significant feeding toxicities to the larvae of the two lepidopteran species. The lethality followed a typical sigmoid dose-mortality pattern with increase of the nematode densities embedded in the capsules. Moisture content in the capsule was critical to the survival of the infective juveniles. More than 80% nematodes could survive above 10% moisture content remained in the capsule. Remaining moisture content within the capsule was dependent on relative humidity, ambient temperature, and capsule size, but not on citric acid reaction time during capsule formation. More than 80% of infective juveniles in the alginate capsules could survive in distilled water at 15$^{\circ}C$ for 60 days. When these nematode capsules containing welsh onion extract as another phagostimulant were applied on the 3rd instar larvae of Sp. exigua infesting peanut plants, they resulted in about 90% control efficacy. These results indicate that the alginate capsulation can be used for leaf-spray agent of the entomopathogenic nematodes as well as for improved storage purpose.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.1
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• pp.7-11
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• 2010

The reduction of optical losses in mono-crystalline silicon solar cell by surface texturing is a critical step to improve the overall cell efficiency. In this study, we have changed the sub-micrometer structure on the micrometer pyramidal structure by 2-step texturing. The Ag particles were coated on the micrometer pyramid surface in $AgNO_3$ solution, and then the etching with hydrogen fluoride and hydrogen peroxide created even smaller nano-pyramids in these pyramids. As a result, we observed that the changes of size and thickness of nano structure on pyramidal surface were determined by $AgNO_3$ concentration and etching time. Using 2-step texturing, the surface of wafers is etched to resemble the rough surface of a lotus leaf. Lotus surface can reduce average reflectance from 10% to below 3%. This reflectance is less than conventional textured wafer including anti-reflection coating.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.10
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• pp.1151-1157
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• 2017

This study examined the immune response of Philippines eel (Anguilla bicolor) to the oral administration of fermented Sparassis crispa stipe extract for 6 weeks. The S. crispa extract fermented with Lactobacillus plantarum showed a higher total phenol content (301.68 ppm) and DPPH radical scavenging activity (63.9%) than those fermented with other strains. Therefore, L. plantarum was selected as a suitable starter culture for the fermentation of S. crispa stipe. The eels were fed a commercial diet supplemented with 1% of fermented S. crispa stipe extract for 6 weeks. The mortality rate of the eels fed the supplemented diet was significantly lower than those of the control after 6 weeks. The lysozyme activity of the serum was increased significantly (12.33 ${\rightarrow}$ 54.66 units) after 6 weeks in the eel fed supplemented diets of fermented S. crispa stipe. The serum of the eel fed the supplemented diet of the S. crispa stipe extract showed higher bactericidal activity. These results suggest that both the S. crispa stipe extract and fermented S. crispa stipe have strong potential to activate the innate immune response of the Philippines eel.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.829-834
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• 2011

Lysozyme in egg white functions as bacteriolysis agent and ovalbumin plays a role as antigen in immune system. Egg white analysis methods usually include electrophoresis, gel permeation chromatography and reversed-phase HPLC(RP-HPLC). Among them, RP-HPLC was selected for rapid analysis and C18 column(Agilent, USA) was used as HPLC column. Optimum conditions were searched by changing mobile phase and temperature. Capacity factor and resolution were calculated and compared for various elution conditions. In the isocratic elution, mobile phase volume ratio was changed from 30/70/0.1 to 60/40/0.1(Acetonitrile(ACN)/Distilled water(DW)/Trifluoroacetic acid(TFA)). ACN composition was increased by 10% and temperature was set as $20^{\circ}C$. In the gradient elution, ACN/DW ratio was changed from 10/90 to 60/40 during 20 minute and temperature was varied as 20, 30 and $40^{\circ}C$. In the isocratic elution, three peaks were separated at 50/50/0.1. Lysozyme and ovalbumin were confirmed as first and third peak in three peaks respectively. In the gradient elution, four peaks were separated at $30^{\circ}C$. Lysozyme and ovalbumin were confirmed as first peak and third peak in four peaks respectively.

• Korean journal of applied entomology
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• v.40 no.3
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• pp.259-264
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• 2001

Toxicological studies of two potential biological control agents, the entomopathogenic nematode (Steinernema carpocapsae) and the symbiotic bacteria (Xenorhabdus nematophilus) were conducted against two beneficial insects and one mammal species. Two microbial agents varied in their toxicities between two insect species: an ant, Pristomyrmex pungens, and silkworm, Bombyx mori. In oral toxicity test, the symbiotic bacteria resulted in significant lethal [half lethal concentration of $1.4$\times$10^3$colony-forming units (cfu)/ml] on the ants, while they gave little lethal effect (half lethal concentration of more than $10^{8}$ cfu/ml) on the silkworms. The nematodes, however, gave significant lethal effect [half lethal concentration of 4 infected juveniles (IJs)/ml] on the silkworms, while they did little lethal effect (half lethal concentration of 150,000 IJs/ml) on the ants in topical assays. Both the nematodes and the bacteria did not give lethal effect to the albino rats, Rattus norvegicus, when they were fed orally into the rats. Also, any of these microbial agents were not detected in the internal organs of the treated rats.

• Korean journal of applied entomology
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• v.36 no.2
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• pp.172-178
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• 1997

There was a great variation in insecticide susceptibilities among field and laboratory populations of the beet armyworm, Spodoptera exigua (Hiibner). Unselected laboratory population, which had been reared for 6-7 generations in our laboratory without exposure to insecticides, was more susceptible than its parental field population in all tested insecticides. Two selected laboratory populations with parathion or deltamethrin showed much higher insecticide tolerance than did the unselected laboratory population in their own selection insecticide. The variation of the insecticide susceptibilities was highly correlated with esterase and acetylcholinesterase activities. Field and the selected laboratory populations had lower acetylcholinesterase activities and higher esterase activities than did the unselected laboratory population. Acetylcholinesterase of the field and the selected laboratory populations had higher Km values than did that of the unselected. In a population, Km values were varied among different developmental stages; acetylcholinesterase of the fifth instar larvae had the highest Km value among those of the other larval stages. Twenty one esterase bands were separated on 6.5% nondenaturing polyacrylamide gel from the whole body extracts of the fifth instar larvae. E2, E7, E8, Ell, El6, and El7 esterase bands were developed more frequently in the insecticides-selected populations than in the unselected population. These results suggest that the variation of insecticide susceptibilities of the beet armyworm includes both biochemical mechanisms: target site insensitivity and enhanced activity of detoxification enzyme.