• 한국식품영양학회지
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• 제10권1호
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• pp.122-126
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• 1997

Bifidobacteria have been known as beneficial inhabitant of human intestine. Therefore, bifidobacteria began to be noticed as a starter in the manufacture of fermented dairy products. Perhaps the key for effective use of bifidobacteria in commercial dairy products is the maintenance of viability of bifidobacteria during large scale preparation of starter culture and distribution of products. So we tried to obtain the bifidobacteria having suitable characteristics for using as a starter in the manufacture of fermented dairy products. Among bifidobacteria isolated from Korean, E-4 strain showed the highest resistance to oxygen. To know whether the selected strain will be fit for manufacture of fermented dairy products, we also investigated resistance of the selected strain to HCI. The selected strain, E-4, was more resistant to environmental stresses such as oxygen, H2O2 and HCI than Bifidobacterium longum known as resistant strain to environmental stresses. According to carbohydrate fermentation patterns and morphological characteristics, E-4 strain was identified as B. bifidum. In conclusion, the selected strain, E-4, was thought to be fit for manufacture of fermented dairy products.

• 미생물학회지
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• 제18권4호
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• pp.161-171
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• 1980

A mutant strain having increased productivity of both enzymes, protease and amylase, was obtained from A. flavus KU 153, isolatd from South Korea for its high protease production by successive ultra-violet light irradiation, Two glucoamylases from the mutant strain selected were purified from wheat branculture by successive salting out, followed by dialysis and column chromatography, and their characteristics were compared with those of the wild strain. Glucoamylase production of the mutant selected was increased about 3.3 times compared with the wild strain, and 2.1 times compared with the parental strain, ${\alpha}-amylase$ activity of the mutant selected was about 2 times hugher than that of the wild strain or the parental strain. Protease and cellulase productivities of the muant selected were all alike compared with those of the highly proteolytic mutant, the parental strain. Therefore, it was considered that the back mutation on the protease production did not occurred in the formation process of the glucoamylase producing mutant. Total activities of glucoamylase I and II from the mutant selected were 2.86 and 3.65 times higher compared with those from the wild strain, respectively. Considering the optimal pH-thermal stability and Km-Vmax value of glucoamylase I and II from both strains, wild and mutant, it was deduced that the characteristics of glucoamylase I and II from the wild strain did not altered during the mutation process. Therefore, it was concluded that the selected mutant did not induce the formation of another glucoamylase isozyme, or the changes in the characteristics of the glucoamylase, but induce the productivity of the same glucoamylase I and II by the action of regulatory gene.

• Journal of Microbiology
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• 제33권2호
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• pp.142-145
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• 1995

The pumb gene encoding a basic amino acid transport protein in Neurospora crassa could be cloned by using a mutant strain defective in pmb gene as a host strain, using a negative selection on the media containing amino acid analogue canavanine. To select positive transformants of the genes for cloning, an auxotrophic marker (his-2) was added to a pmb mutant strain by mating ; a triple mutant (pmn : pmb : his-2) was constructued by crossing a strain defective in basic amino acid transport system (# 1683-bat um 535 "A") to a double mutant strain defective in neutral amino acid transport and histidine production (mitrol : his-2 "a"). Crossing was performed on synthetic crossing (SC) media containing histidine. The pmn : pmb and pmn :pmb : his-2 strains were selected among the progeny colonies from crosses on plates containing 5- .mu.g/ml para-fluoro-phenylalanine (PFPA), 200 .mu.g/ml canavanine, and 500 .mu.g/ml histidine. The selected colonies were cultured on minimal media with or without histidine for discarding pmn : pmb strain, because the pmn : pmb : his -2 strain grows only on histidine containing media. The pmn :pmb : his-2 strain selected can be used as a host strain for the cloning of the pmb and the pmn genes from a Neurospora genomic library by means of positive selections.

• Journal of Life Science
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• 제9권1호
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• pp.14-16
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• 1999

Genetic variability was monitored by random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) in dicofol-susceptible (S), dicofol-resistant (R) and its reverse-selected (RS) strains of two-spotted spider mite, of Tetranychus urticae. Before the reverse-selection, RS strain, selected reversely from R strain, was 23-fold resistance ratio at {TEX}$LC_{50}${/TEX} to S strain. The resistance was started to in incline slowly to the resistance level of S strain after one year, and the resistance ratio was 4-fold in the 7 years after then. PCR-amplification of T. urticae DNA showed polymorphism in the amplifications with 12 primers in 100 kinds of arbitrary DNA sequences. RAPD amplification with primer OPR-12 (5`-ACAGGTGCGT-3`) showed amplified bands at 1,000 base pair in the S-and RS-strain, and at 350 base pair in R-strain. The results of polymorphism are genetic variabilities derived from development and selection of resistance in each strain. The peculiarly amplified fragments were guessed to participate in dicofol resistance. From the analysis of genetic similarity, it is inferred the gene composition of S-and RS-strain is much closer than that of R-strain.

• 한국응용곤충학회지
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• 제33권2호
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• pp.74-80
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• 1994

바퀴에 대한 dichlorvos(DDVP) 약제로 11세대 누대 도태한 계통에 대한 저항성 유발정도, 교차저항성 및 효소활성을 조사한 결과는 반수치사농도 비교시 감수성에 비하여 8.58배 증가하였고 교차정항성은 chlorpyrifos, propowur, fenvalerate 와 permethrin 약제에서 각각 3.35, 4.09, 2.83 및 2.00배의 저항성을 보였으며 효소활성은 filter paper testdptjrka수성 대비 33%가 증가하였고 전기영동시험에서는 4개의 band인 esterase-1,2,4 및 7 band 가 확인되었다.

• 미생물학회지
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• 제18권2호
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• pp.51-58
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• 1980

Mutational experiments were performed to improved to improve the protease productivity of Aspergillus flavus KU 153, which is selected among the wild strains. A UV-induced mutant strain having high protease productivity was obtained by the use of the clear zone method as a simple criterion for a primary screening test. Neutral and alkaline protease activities of hte mutant strain were higher than 1.8 times, comopared with those of the parental strain, respectively, while in the case of acid protease, it was 2.7 times. The mutant strain selected was more powerful in the production of cellulase and amylase, as well s protease in wheat bran, compared with those of the parental strain. protease production of the parental strain has reached maximum level at 3 days culture, while alkaline nad neutral protease production of the mutantstrain has reached at 2 days culture. On the other hand, the mutant strain formed the spore slowly, compared with the parental strain. Column chromatography of the neutral protease on DEAE-Sephadex A-50 showed that the mutant strain was not induced the formation of another neutral protease isozyme, but induced the variation in the function of regulatory gene.

• 미생물학회지
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• 제9권1호
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• pp.27-31
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• 1971

This experiment was carried out to research for the use of the mycelium and enzyme on the production of fermented feed. Among 354 strains isolated from natural sources, 3 strains of useful yeasts were selected and identified, and the cultural conditions of these strains were examined. The results obtained were as follows. 1) The strian No.55, No.112 and No. 340 selected were identified Endomycopsis fibuliger, Endomycopsis javanensis and Candida tropicalis, respectively. 2) The optimum pH and sugar concentration of the medium for the strain No.55, No.112 and 340 selected was around pH 6.5and Bllg.10.deg.. The optimum temperature for the growth of the strain No.55 and No.112 selected was 30.deg.C and was 25.deg.C of strain No.340. 3) The strain No.55 and No.112 were grown exceedingly well on the media containing 0.1 percent of (NH/sub 4/)/sub 2/SO/sub 4/.

• 한국응용곤충학회지
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• 제28권1호
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• pp.23-27
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• 1989

Pyrethroid계 살충제인 cypermethrin과 carbamate계 살충제인 pirimicarb를 공시하여 실내 감수성계통 복숭아혹진닷물(Myzus persicae)을 인위적으로 루대도태한 후, 저항성 발달속도와 정도를 조사하고, 이들 저항성 계통의 타살충제에 대한 교차저항성 유무와 그 정도를 검토하였다. 저항성 발달속도는 cypermethrin 20세대 도태계통에서 도태전에 비하여 20.5차 증가하였으나, pirimicarb 20세대 도태계통에서는 3.2배 증가에 그쳐 살충제 종류에 따라 큰 차이를 보였다. Cypermethrin 도태계통은 acephate와 pirimicarb에 대해서 , pirimicarb 도태계통은 acephate와 cypermethrin에 대해서 교차저항성을 나타내었다. 그러나 cypermethrin, pirimicarb 도태계통은 demeton-S-methyl에 대해서 비교우저항성을 나타내었다.

• Journal of Microbiology and Biotechnology
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• 제3권2호
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• pp.95-98
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• 1993

This study was carried out to isolate and characterize the mutant strains of Schwanniomyces castellii NRRL Y-2477. Mutants were prepared with the treatment of ethyl methane sulfonate. 2-deoxy-D-glucose resistant mutants were isolated and two mutants were selected based on their high production of amylolytic enzymes and their ability to ferment starch. The mutants selected had higher a-amylase and glucoamylase activities than the wild type strain from several other carbon sources. Especially, it was revealed that mutant strain M-9, when cultured in the presence of glucose as a sole carbon source, shows relatively high activities of a-amylase and glucoamylase compared to those of the wild type strain. In result, this mutant strain can be considered as a constitutive producer of amylolytic enzymes. To compare the ethanol production ability of wild type strain and of mutant strains selected, an alcohol fermentation was carried out using 100 g/l soluble starch. Mutant strain M-9 did not improve the direct alcohol fermentation of starch, despite its excellent amylolytic activities performance. On the other hand, mutant strain M-6 produced 37.9 g/l (4.8%, v/v) ethanol by utilizing about 82% of substrate.

• 한국응용곤충학회지
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• 제29권3호
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• pp.194-200
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• 1990

Pyrethroid계 살충제 fenvalerate를 공시하여 실내 감수성계통 배추좀나방(Plu tella xylostella L.)을 인위적으로 누대도태한 후 저항성 발달속도와 정도를 조사하고, 이 저항성계통의 타 살충제에 대한 교차저항성 유무와 정도를 검토하였다. 저항성 발달속도는 fenvalerate 24세대 도태계통에서 도태전에 비하여 66.2배 증가하였다. Fenvalerate 도태계통은 pyrethroid계 살충제인 deltamethrin에 145배의 고도의 교차저항성을 나타내었고, alphamethrin, cypermethrin, fenvalerate, permethrin, tetramethrin에 17.4 -45.0배의 교차저항성을 나타내었다. 유기인계 diazinon, dichlorvos, ethoprophos, EPN과 카바메이트계 BPMC, carbaryl, methorny I에서는 2.1-4.3배의 낮은 교차저항성을 나타내었다. 그러나, 유기인계의 acephate, fenitrothion과 카바메트계 carbofuran에 대해서 비교차저항성을 나타내었다.