• Journal of Microbiology and Biotechnology
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• 제22권3호
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• pp.331-338
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• 2012

A novel gene coding for an endo-${\beta}$-1,4-mannanase (manA) from Bacillus subtilis strain G1 was cloned and overexpressed in P. pastoris GS115, and the enzyme was purified and characterized. The manA gene consisted of an open reading frame of 1,092 nucleotides, encoding a 364-aa protein, with a predicted molecular mass of 41 kDa. The ${\beta}$-mannanase showed an identity of 90.2-92.9% ${\leq}95%$) with the corresponding amino acid sequences from B. subtilis strains deposited in GenBank. The purified ${\beta}$-mannanase was a monomeric protein on SDS-PAGE with a specific activity of 2,718 U/mg and identified by MALDI-TOF mass spectrometry. The recombinant ${\beta}$-mannanase had an optimum temperature of $45^{\circ}C$ and optimum pH of 6.5. The enzyme was stable at temperatures up to $50^{\circ}C$ (for 8 h) and in the pH range of 5-9. EDTA and most tested metal ions showed a slightly to an obviously inhibitory effect on enzyme activity, whereas metal ions ($Hg^{2+}$, $Pb^{2+}$, and $Co^{2+}$) substantially inhibited the recombinant ${\beta}$-mannanase. The chemical additives including detergents (Triton X-100, Tween 20, and SDS) and organic solvents (methanol, ethanol, n-butanol, and acetone) decreased the enzyme activity, and especially no enzyme activity was observed by addition of SDS at the concentrations of 0.25-1.0% (w/v) or n-butanol at the concentrations of 20-30% (v/v). These results suggested that the ${\beta}$-mannanase expressed in P. pastoris could potentially be used as an additive in the feed for monogastric animals.

• Advances in nano research
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• 제6권2호
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• pp.183-200
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• 2018

In the present study silver nanoparticles (AgNPs) were successfully synthesized using aqueous extract of Sargassum muticum. The aqueous extract (10%) treated with 1 mM silver nitrate solution resulted in the formation of AgNPs and the surface plasmon resonance (SPR) of the formed AgNPs was recorded at 360 nm using UV-Visible spectrophotometer. The molecules involved in the formation of AgNPs were identified by Fourier transform infrared spectroscopy (FT-IR), surface morphology was studied by using scanning electron microscopy (SEM), SEM micrograph clearly revealed the size of the AgNPs was in the range of 40-65 nm with spherical, hexagonal in shape and poly-dispersed nature, and X-ray diffraction spectroscopy (XRD) was used to determine the crystalline structure. High positive Zeta potential (36.5 mV) of formed AgNPs indicates the stability and XRD pattern revealed the crystal structure of the AgNPs by showing the Bragg's peaks corresponding to (111), (200), (311) and (222) planes of face-centered cubic crystal phase of silver. The synthesized AgNPs exhibited effective anticancerous activity (at doses 25 and $50{\mu}g/ml$ of AgNPs) against Breast cancer cell line (MCF7).

• 자원리싸이클링
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• 제30권4호
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• pp.11-19
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• 2021

황화 광석으로부터 유래된 고농도 비소 함유 침출 용액에 대하여 공기와 활성탄 병용을 통해 비소를 산화 및 침전 제거하는 연구를 수행하였다. 침출 용액은 국내 황화 광석 시료를 pH 1, 50℃ 조건의 황산 용액에서 95시간동안 침출하여 제조하였으며, 침출 용액 내 금속이온 농도 분석 결과 Fe가 약 7 g/L, As가 약 3 g/L 함유된 것으로 측정되었다. 해당 용액에 대하여 공기와 활성탄 병용 시 비소의 산화 및 침전 효과를 파악하기 위해 5가지 산화 조건(공기 주입, 공기와 1, 5, 10 w/v% 활성탄 투입, H₂O₂ 투입) 하에 초기 pH 1, 90℃에서 72시간 동안 산화 및 침전 실험을 수행하였다. 실험 결과 공기와 활성탄을 함께 투입한 경우 활성탄 표면에 생성된 작용기로 인해 산화 반응의 속도가 빠르고 비소 제거율이 향상되는 것으로 분석되었다. 또한, 활성탄의 투입량이 증가할수록 반응의 효율이 향상되었으며, 5 w/v% 이상의 활성탄 투입 시 약 93-94%의 비소가 제거된 것으로 분석되었다. 침전 생성물에 대한 XRD 분석 결과 산화 반응에 의해 스코로다이트(FeAsO₄·2H₂O)가 잘 생성된 것으로 나타났다.

• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1633-1637
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• 2019

While considering the photon attenuation coefficient (${\mu}$) and its related parameters for photons shielding, it is necessary to account for its transmitted and reflected photons energy spectra and dose contribution. Monte Carlo simulation was used to study the efficiency of clay ($1.99g\;cm^{-3}$) as a shielding material below 150 keV photon. Am-241 gamma source and an X-ray of 150 kVp were calculated. The calculated value of ${\mu}$ for Am-241 is higher within 5.61% compared to theoretical value for a single-energy photon. The calculated half-value layer (HVL) is 0.9335 cm, which is lower than that of ordinary concrete for X-ray of 150 kVp. A thickness of 2 cm clay was adequate to attenuate 90% and 85% of the incident photons from Am-241 and X-ray of 150 kVp, respectively. The same thickness of 2 cm could shield the gamma source dose rate of Am-241 (1 MBq) down to $0.0528{\mu}Sv/hr$. For X-ray of 150 kVp, photons below 60 keV were significantly decreased with 2 cm clay and a dose rate reduction by ~80%. The contribution of reflected photons and dose from the clay is negligible for both sources.

• 한국응용곤충학회지
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• 제21권2호
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• pp.78-86
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• 1982

자두 살구나무에 기생하는 나무좀의 종류와 생태를 조사하였던 결과를 요약하면 다음과 같다. 1. 자두살구나무를 하는 나무좀은 서울나무좀 (Scolytus seulensis), 뽕나무좀(Xyleborus atratus), 오리나두좀(X. germanus, 붉은목나무좀(X. rubricollis) 및 감나무좀(X. saxeseni)을 채집하였고 기주로는 서울나무좀은 자두와 살구나무에 뽕나무좀 오리나무좀, 감나무좀은 살구, 밤나무에 붉은목나무좀은 자두, 밤나무등에 각각 침입함을 확인하였는데 자두, 살구나무에 발생량과 피해가 심한 종은 서울나무좀이었다. 2. 서울나무좀의 발생소장을 보면 1980년 7월 10일과 8월 25일 1981년에는 7월 15일과 8월 20일로 1화기는 7월 중순에 2화기는 8월 하순의 1년 2회로 추정되었다. 3. 살구품종중 서울나무좀에 의한 m당 충공수는 Henderson(Apricot)과 V-49057(Apricot)은 100개 이상이었으며 Derbyroyal(Apricot)은 12개 이하로 적었다. 대체로 한국재래종과 일본계도입종들에 비하여 구주계품종에 치해공이 많았고 방향별 차이는 적었으나 동서남북순이었으며 모공의 길이가 길수로 유충공수도 많았다. 4. 성충의 교미는 $27^{\circ}C$ 내외가 많았으며 5.6월의 교미는 7.8월에 비하여 교미시간이 다소 길었다. 5. 자두나무 과실중의 변화는 피해주에서 개화 4주일 후인 6월 23일에 12.25g으로서 과중증가가 없었으나 건전주의 과실은 6월 23일에 32.23gr이었고 수확기인 7월 7일에는 63.5gr이었다. 6. 서울나무좀의 천적으로 어깨넓적좀벌과의 일종인 Eurytoma sp.를 서울나무좀의 노숙유충이나 용에서 용상태로 발생하였고 5월 초부터 6월 25일 사이에 우화하였으며 성충의 일주일 내외였다.

• Nuclear Engineering and Technology
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• 제53권6호
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• pp.2000-2010
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• 2021

Mechanical moduli, such as Young's modulus (E), Bulks modulus (B), Shear modulus (S), longitudinal modulus (L), Poisson's ratio (σ) and micro Hardness (H) were theoretically calculated for (100-x)TeO₂+x MgO glasses, where x = 10, 20, 30, 40 and 45 mol%, based on the Makishima-Mackenzie model. The estimated results showed that the mechanical moduli and the microhardness of the glasses were improved with the increase of the MgO contents in the TM glasses, while Poisson's ratio decreased with the increase in MgO content. Moreover, the radiation shielding capacity was evaluated for the studied TM glasses. Thus, the linear attenuation coefficient (LAC), mass attenuation coefficient (MAC), transmission factor (TF) and half-value thickness (𝚫_0.5) were simulated for gamma photon energies between 0.344 and 1.406 MeV. The simulated results showed that glass TM10 with 10 mol % MgO possess the highest LAC and varied in the range between 0.259 and 0.711 cm^-1, while TM45 glass with 45 mol % MgO possess the lowest LAC and vary in the range between 0.223 and 0.587 cm^-1 at gamma photon energies between 0.344 and 1.406 MeV. Furthermore, the BXCOM program was applied to calculate the effective atomic number (Z_eff), equivalent atomic number (Z_eq) and buildup factors (EBF and EABF) of the glasses. The effective removal cross-section for the fast neutrons (ERCSFN, ∑_R) was also calculated theoretically. The received data depicts that the lowest ∑_R was achieved for TM10 glasses, where ∑_R = 0.0193 cm² g^-1, while TM45 possesses the highest ERCSFN where ∑_R = 0.0215 cm² g^-1.

• Carbon letters
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• 제24권
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• pp.73-81
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• 2017

Interconnected meso/microporous activated carbons were prepared from pumpkin seeds using a simple chemical activation method. The porous carbon materials were prepared at different temperatures (PS-600, PS-700, PS-800, and PS-900) and demonstrated huge surface areas ($645-2029m^2g^{-1}$) with excellent pore volumes ($0.27-1.30cm^3g^{-1}$). The well-condensed graphitic structure of the prepared activated carbon materials was confirmed by Raman and X-ray diffraction analyses. The presence of heteroatoms (O and N) in the carbon materials was confirmed by X-ray photoemission spectroscopy. High resolution transmission electron microscopic images and selected area diffraction patters further revealed the porous structure and amorphous nature of the prepared electrode materials. The resultant porous carbons (PS-600, PS-700, PS-800, and PS-900) were utilized as electrode material for supercapacitors. To our delight, the PS-900 demonstrated a maximum specific capacitance (Cs) of $303F\;g^{-1}$ in 1.0 M $H_2SO_4 $ at a scan rate of 5 mV. The electrochemical impedance spectra confirmed the poor electrical resistance of the electrode materials. Moreover, the stability of the PS-900 was found to be excellent (no significant change in the Cs even after 6000 cycles).

• Journal of Industrial and Engineering Chemistry
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• 제68권
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• pp.180-186
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• 2018

We report the discovery of Li-rich $Li_{1+x}[(Ni_{0.225}Co_{0.15}Mn_{0.625})_{1-y}V_y]O_2$ as a cathode material for rechargeable lithium-ion batteries in which a small amount of tetravalent vanadium ($V^{4+}$) is selectively and completely incorporated into the manganese sites in the lattice structure. The unwanted oxidation of vanadium to form a $V_2O_5-like$ secondary phase during high-temperature crystallization is prevented by uniformly dispersing the vanadium ions in coprecipitated $[(Ni_{0.225}Co_{0.15}Mn_{0.625})_{1-y}V_y](OH)_2$ particles. Upon doping with $V^{4+}$ ions, the initial discharge capacity (>$275mA\;h\;g^{-1}$), capacity retention, and voltage decay characteristics of the Li-rich layered oxides are improved significantly in comparison with those of the conventional undoped counterpart.

• 한국미생물·생명공학회지
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• 제22권6호
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• pp.665-671
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• 1994

For the production of pyrogallot from gallic acid, about 100 strains of bacteria capable of assimilating gallic acid as a sole carbon and energy source were isolated from the soil. JH- 004 strain showing the highest activity of gallate decarboxy#lase was selected from them and identi- fied as Erwinia sp. The optimal conditions for the production of pyrogallol from gallic acid were examined. The resting cells of JH-004 cultured in a complex medium containing 0.2%(w/v) gallic acid were prepared after the treatment of the pellet with a freezing and thawing, and used as a enzyme source. The reaction mixtures for the maximal production of pyrogallol were shown to be 6 g/l of resting cells and 15 g/l of gallic acid in 25 mM potassium phosphate buffer. The optimal pH for the reaction was 5.0 and the optimal temperature was 35$\circ$C . Additionally, Triton X-100(0.01%, w/v) was found to be most effective for the production of pyrogallol. Under the above conditions, 10.27 g/l of pyrogallol was produced from 15 g/l of gallic acid after incubation of 35 hrs. This amount of pyrogallol corresponds to a 92.37% yields, based on gallic acid.

• Bulletin of the Korean Chemical Society
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• 제30권4호
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• pp.783-786
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• 2009

Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and ion chromatography(IC) were employed to analyze the thermal behavior of $Li_xCoO_2$ cathode material of lithium ion battery. The mass loss peaks appearing between 60 and 125 ${^{\circ}C}$ in TGA and the exothermic peaks with 4.9 and 7.0 J/g in DSC around 75 and 85 ${^{\circ}C}$ for the $Li_xCoO_2$ cathodes of 4.20 and 4.35 V cells are explained based on disruption of solid electrolyte interphase (SEI) film. Low temperature induced HF formation through weak interaction between organic electrolyte and LiF is supposed to cause carbonate film disruption reaction, $Li_2CO_3\;+\;2HF{\rightarrow}\;2LiF\;+\;CO_2\;+\;H_2O$. The different spectral DSC/TGA pattern for the cathode of 4.5 V cell has also been explained. Presence of ionic carbonate in the cathode has been identified by ion chromatography and LiF reported by early researchers has been used for explaining the film SEI disruption process. The absence of mass loss peak for the cathode washed with dimethyl carbonate (DMC) implies ionic nature of the film. The thermal behavior above 150 ${^{\circ}C}$ has also been analyzed and presented.