• Applied Biological Chemistry
• /
• 제42권3호
• /
• pp.181-187
• /
• 1999

경주지역의 토양으로부터 Fusarium 속 식물병원균에 길항력을 갖는 chitinase 생산성 길항미생물을 분리할 수 있었으며, 이를 분류학적으로 동정하여 본 결과 Serratia proteamaculans 3095로 동정할 수 있었다. 이 균주가 생성하는 chitinase의 생성조건을 조사한 결과 탄소원으로 colloidal chitin이 가장 좋았으며 그 최적 농도는 0.15%이었고, glucose에 의해 chitinase 생산 유도를 억제받는 효소임을 알 수 있었다. 질소원에 의한 영향은 $(NH_4)_2SO_4,\;(NH_4)Cl$, peptone 등에 의해 chitinase 생산성이 증가되었고, $(NH_4)_2SO_4$와 peptone을 각각 0.1%씩 첨가하였을 때 chitinase 생산이 가장 좋았다. 또한 시드름병균 Fusarium oxysporum을 대상으로 in vitro, in vivo pot 실험을 통해 Serratia sp. 3095의 강한 방제력을 검증할 수 있었다.

• Structural Engineering and Mechanics
• /
• 제63권1호
• /
• pp.1-9
• /
• 2017

Shot peening is a cold surface treatment employed to induce residual stress field in a metallic component beneficial for increasing its fatigue strength. The experimental investigation of parameters involved in shot peening process is very complex as well as costly. The most attractive alternative is the explicit dynamics finite element (FE) analysis capable of determining the shot peening process parameters subject to the selection of a proper material's constitutive model and numerical technique. In this study, Ansys / LS-Dyna software was used to simulate the impact of steel shots of various sizes on an aluminium alloy plate described with strain rate dependent elasto-plastic material model. The impacts were carried out at various incident velocities. The influence of shot velocity and size on the plastic deformation, compressive residual stress and force-time response were investigated. The results exhibited that increasing the shot velocity and size resulted in an increase in plastic deformation of the aluminium target. However, a little effect of the shot velocity and size was observed on the magnitude of target's subsurface compressive residual stress. The obtained results were close to the published ones, and the numerical models demonstrated the capability of the method to capture the pattern of residual stress and plastic deformation observed experimentally in aluminium alloys. The study can be quite helpful in determining and selecting the optimal shot peening parameters to achieve specific level of plastic deformation and compressive residual stress in the aluminium alloy parts especially compressor blades.

• Journal of Microbiology and Biotechnology
• /
• 제28권5호
• /
• pp.697-706
• /
• 2018

Lactobacillus pentosus K1-23 was selected from among 25 lactic acid bacterial strains owing to its high inhibitory activity against several pathogenic bacteria, including Escherichia coli, Salmonella typhimurium, S. gallinarum, Staphylococcus aureus, Pseudomonas aeruginosa, Clostridium perfringens, and Listeria monocytogenes. Additionally, among 13 strains of Aureobasidium spp., A. pullulans NRRL 58012 was shown to produce the highest amount of ${\beta}$-glucan ($15.45{\pm}0.07%$) and was selected. Next, the optimal conditions for a solid-phase mixed culture with these two different microorganisms (one bacterium and one yeast) were determined. The optimal inoculum sizes for L. pentosus and A. pullulans were 1% and 5%, respectively. The appropriate inoculation time for L. pentosus K1-23 was 3 days after the inoculation of A. pullulans to initiate fermentation. The addition of 0.5% corn steep powder and 0.1% $FeSO_4$ to the basal medium resulted in the increased production of lactic acid bacterial cells and ${\beta}$-glucan. The following optimal conditions for solid-phase mixed culture were also statistically determined by using the response surface method: $37.84^{\circ}C$, pH 5.25, moisture content of 60.82%, and culture time of 6.08 days for L. pentosus; and $24.11^{\circ}C$, pH 5.65, moisture content of 60.08%, and culture time of 5.71 days for A. pullulans. Using the predicted optimal conditions, the experimental production values of L. pentosus cells and ${\beta}$-glucan were $3.15{\pm}0.10{\times}10^8CFU/g$ and $13.41{\pm}0.04%$, respectively. This mixed culture may function as a highly efficient antibiotic substitute based on the combined action of its anti-pathogenic bacterial and immune-enhancing activities.

• Journal of Microbiology and Biotechnology
• /
• 제25권2호
• /
• pp.196-205
• /
• 2015

A Sulfolobus-E. coli shuttle vector for an efficient expression of the target gene in S. acidocaldarius strain was constructed. The plasmid-based vector pSM21 and its derivative pSM21N were generated based on the pUC18 and Sulfolobus cryptic plasmid pRN1. They carried the S. solfataricus P2 pyrEF gene for the selection marker, a multiple cloning site (MCS) with C-terminal histidine tag, and a constitutive promoter of the S. acidocaldarius gdhA gene for strong expression of the target gene, as well as the pBR322 origin and ampicillin-resistant gene for E. coli propagation. The advantage of pSM21 over other Sulfolobus shuttle vectors is that it contains a MCS and a histidine tag for the simple and easy cloning of a target gene as well as one-step purification by histidine affinity chromatography. For successful expression of the foreign genes, two genes from archaeal origins (PH0193 and Ta0298) were cloned into pSM21N and the functional expression was examined by enzyme activity assay. The recombinant PH0193 was successfully expressed under the control of the gdhA promoter and purified from the cultures by His-tag affinity chromatography. The yield was approximately 1 mg of protein per liter of cultures. The enzyme activity measurements of PH0913 and Ta0298 revealed that both proteins were expressed as an active form in S. acidocaldarius. These results indicate that the pSM21N shuttle vector can be used for the functional expression of foreign archaeal genes that form insoluble aggregates in the E. coli system.

• 한국철도학회논문집
• /
• 제17권1호
• /
• pp.52-58
• /
• 2014

노반 성토체에서 발생하는 소성 변형은 콘크리트 궤도의 안정성과 유지보수에 영향을 미친다. 철도 노반에서의 장기적인 소성 변형은 주로 반복적인 열차 통과로 발생하는 누적된 비탄성적 변형률에 의해 발생한다. 누적 소성 변형의 예측은 궤도의 유지보수와 열차의 안전한 운영을 위해서 중요하다. 본 연구에서는 서로 다른 강화노반 두께를 가진 철도노반에서 발생하는 연직 변위를 계산하였다. 누적 소성 변형률을 계산하기 위한 멱함수의 상수는 삼축 실험과 실대형 재하 실험의 결과로부터 구하였다. 표준 노반 단면에 대한 3차원 유한요소해석 결과로부터 강화노반의 두께를 선정하는 가이드라인을 제시하였다.

• Mycobiology
• /
• 제43권1호
• /
• pp.81-86
• /
• 2015

To promote the selection of promising monokaryotic strains of button mushroom (Agaricus bisporus) during breeding, 61 progeny strains derived from basidiospores of two different lines of dikaryotic parental strains, ASI1038 and ASI1346, were analyzed by nucleotide sequencing of the intergenic spacer I (IGS I) region in their rDNA and by extracellular enzyme assays. Nineteen different sizes of IGS I, which ranged from 1,301 to 1,348 bp, were present among twenty ASI1346-derived progeny strains, while 15 different sizes of IGS I, which ranged from 700 to 1,347 bp, were present among twenty ASI1038-derived progeny strains. Phylogenetic analysis of the IGS sequences revealed that different clades were present in both the ASI10388- and ASI1346-derived progeny strains. Plating assays of seven kinds of extracellular enzymes (${\beta}$-glucosidase, avicelase, CM-cellulase, amylase, pectinase, xylanase, and protease) also revealed apparent variation in the ability to produce extracellular enzymes among the 40 tested progeny strains from both parental A. bisporus strains. Overall, this study demonstrates that characterization of IGS I regions and extracellular enzymes is useful for the assessment of the substrate-degrading ability and heterogenicity of A. bisporus monokaryotic strains.

• Mycobiology
• /
• 제44권3호
• /
• pp.155-161
• /
• 2016

The most economically important species used in a wide range of fermentation industries throughout Asia belong to Aspergillus section Flavi, which are morphologically and phylogenetically indistinguishable, with a few being toxigenic and therefore a major concern. They are frequently isolated from Korean fermentation starters, such as nuruk and meju. The growing popularity of traditional Korean alcoholic beverages has led to a demand for their quality enhancement, therefore requiring selection of efficient non-toxigenic strains to assist effective fermentation. This study was performed to classify the most efficient strains of Aspergillus section Flavi isolated from various types of traditional wheat nuruk, based on a polyphasic approach involving molecular and biochemical evaluation. A total of 69 strains were isolated based on colony morphology and identified as Aspergillus oryzae/flavus based on internal transcribed spacer and calmodulin gene sequencing. Interestingly, none were toxigenic based on PCR amplification of intergenic regions of the aflatoxin cluster genes norB-cypA and the absence of aflatoxin in the culture supernatants by thin-layer chromatography analysis. Saccharification capability of the isolates, assessed through ${\alpha}-amylase$ and glucoamylase activities, revealed that two isolates, TNA24 and TNA15, showed the highest levels of activity. Although the degrees of variation in ${\alpha}-amylase$ and glucoamylase activities among the isolates were higher, there were only slight differences in acid protease activity among the isolates with two, TNA28 and TNA36, showing the highest activities. Furthermore, statistical analyses showed that ${\alpha}-amylase$ activity was positively correlated with glucoamylase activity (p < 0.001), and therefore screening for either was sufficient to predict the saccharifying capacity of the Aspergillus strain.

• 한국약용작물학회지
• /
• 제11권5호
• /
• pp.358-363
• /
• 2003

미치광이풀의 모상근 뱌양에 의해 의학적으로 중요한 물질인 scopolamine과 hyoscyamine 생산을 증진시키기 위해 3종의 곰팡이와 1종의 효모 유래의 생물학적 elicitor를 supernatant와 homogenate의 형태로 처리하였다. Elicitor 중 Candida albicans는 supernatant와 homogenate 모두 scopolamine 생산성을 증가시켰다. Fusarium solani의 homogenate와 C. albicans의 supernatant 처리로 hyoscyamine 함량이 증가되었다. 그러나 나머지 fungus strain도 대조구에 비해 tropane alkaloids의 생산을 다소 증가시켰다. 본 연구에서는 C. albicans가 tropane alkaloids 생산에 적합한 elicitor임으로 구명되었다. 본 연구 결과는 미치광이풀 모상근 대량배양에 의한 tropane alklaoids 대량생산에 기여할 것이다.

• Biomolecules & Therapeutics
• /
• 제3권2호
• /
• pp.122-131
• /
• 1995

Five human cancer cell lines (HeLa S3, Hep 3B, KATO III, Hs 683, HeLa MR) and one human normal cell line (WI-38) were examined cell viability, northern blot analysis, western blot analysis, and in situ hybridization for the expression $O_{6}$ -methylguanine-DNAmethyltransferase (MGMT), which can repair $O_{6}$ -methylguanine produced in DNA by alkylating agents. In cell viability test, the lethal sensitivities of each strain against anti-tumor drug N,N-bis(2-chloroethyl)- N-nitrosourea (BCNU) were counted, and both BCNU treated and untreated cell extracts were examined for their MGMT inducibility by RNA dot blot analysis. Cell lines did not show MGMT induction by BCNU pretreatment. Tlle MGMT activity was assayed by measuring the $^3$H radioactivity transferred from the substrate DNA containing [methyl-$^3$H)-O$_{6}$ -methylguanine to acceptor molecules in the cell extracts. Extracts from the majority of tumor strains and normal cells contained substantial MGMT activity of varying degree, while the known Mer$^{[-10]}$ cell (lacked or severely depleted in MGMT activity) Hela MR, and Hs 683 (proved to be Mer$^{[-10]}$ ) were much more sensitive to BCNU than the rest of tumor strains, as measured by cell viability test. Overall results above, KATO III showed the highest expression level of MGMT among the strains examined. Furthermore, with all the tumor and normal strains tested, a good correlation was observed between MGMT expression and cellular resistance to BCNU. The varying levels of expression of MGMT in human cancer cells found in this study should provide a molecular basis for MGMT expression among tumor strains from different tissue origin, the information of antitumor agents selection for chemotherapy of cancers.

• Journal of Plant Biotechnology
• /
• 제38권4호
• /
• pp.308-314
• /
• 2011

Efficient transformation and regeneration methods are a priority for successful application of genetic engineering to vegetative propagated plants such as grape. In this study, methods for Agrobacterium tumefaciens-mediated transformation and plant regeneration of grapevine (Vitis vinifera) were evaluated. Tamnara, Heukgoosul, Heukbosek, Rizamat were co-cultivated with Agrobacterium strains, LBA4404 containing the vector pBI121 carrying with CaMV 35S promoter, GUS gene as reporter gene and resistance to kanamycin as selective agent. Seven percent of the maximum regeneration frequency was obtained from co-cultivated with explants from Rizamat with LBA4404 strain on selection medium with kanamycin. The addition of acetosyringone, 200 ${\mu}m$ in virulence induction step was a key factor for successful GUS reporter gene expression in grapevine transformation. Transgenic plants showed resistance to kanamycin and the GUS positive response in leaf ($T_0$) stem ($T_0$) and petiole ($T_0$).