• Journal of Microbiology and Biotechnology
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• 제17권5호
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• pp.721-727
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• 2007

Stability-enhanced mutants, H44, 11-94, 5A2-84, and F8, of L-threonine aldolase(L-TA) from Streptomyces coelicolor A3(2)(SCO1085) were isolated by an error-prone PCR followed by a high-throughput screening. Each of these mutant, had a single amino acid substitution: H177Y in the H44 mutant, A169T in the 11-94 mutant, D104N in the 5A2-84 mutant and F18I in the F8 mutant. The residual L-TA activity of the wild-type L-TA after a heat treatment for 20 min at $60^{\circ}C$ was only 10.6%. However, those in the stability-enhanced mutants were 85.7% for the H44 mutant, 58.6% for the F8 mutant, 62.1% for the 5A2-84 mutant, and 67.6% for the 11-94 mutant. Although the half-life of the wild-type L-TA at $63^{\circ}C$ was 1.3 min, those of the mutant L-TAs were longer: 14.6 min for the H44 mutant, 3.7 min for the 11-94 mutant, 5.8 min for the 5A2-84 mutant, and 5.0 min for the F8 mutant. The specific activity did not change in most of the mutants, but it was decreased by 45% in the case of mutant F8. When the aldol condensation of glycine and 3,4-dihydroxybenzaldehyde was studied by using whole cells of Escherichia coli containing the wild-type L-TA gene, L-threo-3,4-dihydroxyphenylserine(L-threo-DOPS) was successfully synthesized with a yield of 2.0 mg/ml after 20 repeated batch reactions for 100 h. However, the L-threo-DOPS synthesizing activity of the enzyme decreased with increased cycles of the batch reactions. Compared with the wild-type L-TA, H44 L-TA kept its L-threo-DOPS synthesizing activity almost constant during the 20 repeated batch reactions for 100 h, yielding 4.0 mg/ml of L-threo-DOPS. This result showed that H44 L-TA is more effective than the wild-type L-TA for the mass production of L-threo-DOPS.

• 한국식품과학회지
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• 제22권4호
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• pp.426-433
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• 1990

Bacillus subtilis HP-4의 ${\beta}-galactosidase$를 추출, 정제하여 효소의 고정화조건 및 고정화 효소의 특성을 조사하였다. B. subtilis를 배양하여 얻은 조효소액을 acetone분획 DEAE-cellulose에 의한 ion exchange chromatography, Sephadex G-100에 의한 gel filtration과정을 통하여 정제하였던 바 약 68% 정제되었으며, 이때의 회수율은 19.9%이었다. 본 효소의 최적 고정화조건은 2%(w/v)의 sodium alginate농도, 15%(v/v)의 효소농도, 그리고 2%,(w/v)의 $CaCl_2$ 농도에서 2시간 교반하였을 때 이었다. 고정화 효소의 최적온도와 pH값은 각각 $55^{\circ}C$와 6.5이었다. 고정화 효소의 활성은 Hg이온과 Cu이온에 의하여 저해되었으며, EDTA, 2-mercaptoethanol, KCN 등의 금속이온 그리고 보호제에 의한 영향은 없었다. 고정화 효소의 ONPG와 유당에 대한 $K_m$값과 $V_{max}$값은 각각 $1.82{\times}10^{-2}M$과 $2.94{\times}10^{-2}M$ 그리고 $3.57{\times}10^{-8}mole/min$과 $1.68{\times}10^{-7}mole/min$이었다. 고정화 효소를 $4^{\circ}C$에서 40일간 저장 후 잔존활성과 5회 재사용 후 잔존활성을 조사한 결과는 각각 95%와 81%이었으며, 탈지유(4.8% 유당)와 5% 유당용액에서 $50^{\circ}C$, 9시간 반응시켰을 때 유당분해율은 각각 51%와 43%이었다.

• Asian-Australasian Journal of Animal Sciences
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• 제13권8호
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• pp.1068-1075
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• 2000

A study involving nutrient balances and radioisotope labeling techniques was undertaken to study energy and protein metabolism, and glucose kinetics of female crossbred Etawah goats, using 12 weaned (BW $14.0{\pm}2.0kg$), 12 late pregnant (BW $27.8{\pm}1.8kg$) and 12 first lactation does (BW $25.0{\pm}5.0kg$). Each class of animal was randomly allotted into 3 dietary treatment groups R1, R2 and R3, that received 100%, 85%, and 70% of ad libitum feed. The rations offered were pellets containing 21.8% CP and 19.3 MJ GE/kg, except for the lactating does who received pellets (17.2% CP and 18.9 MJ GE/kg) and fresh Penisetum purpureum grass. Energy and nitrogen balance studies were conducted during a two-week trial. Daily heat production (HP, estimated by the carbon dioxide entry rate technique), glucose pool and flux were measured. Equations were found for metabolizable energy (ME) and protein intake (IP) requirements for growing goats: ME (MJ/d)=1.87+0.55 RE-0.001 ADG+0.044 RP $(R^2=0.89)$ and IP (g/d)=48.47+2.99 RE+0.029 ADG+0.79 RP $(R^2=0.90)$; for pregnant does: ME (MJ/d)=5.92+0.96 RE-0.002 ADG+0.003 RP $(R^2=0.99)$ and IP (g/d)=58.34+5.41 RE+0.625 ADG-0.30 RP $(R^2=0.98)$; and for lactating does: ME (MJ/d)=4.23+0.713 RE+0.003 ADG+0.006 RP+0.002 MY $(R^2=0.86)$; IP (g/d)=84.05-5.36 RE+0.055 ADG-0.16 RP+0.068 MY $(R^2=0.45)$, where RE is retained energy (MJ/d), ADG is average daily gain in weight (g/d), RP is retained protein (g/d) and MY is milk yield (ml/d). ME and IP requirements for maintenance for growing goats were 0.46 MJ/d.kg $BW^{0.75}$ and 7.43 g/d.kg $BW^{0.75}$, respectively. Values for the pregnant and lactating does were in the same order, 0.55 MJ/d.kg $BW^{0.75}$ and 11.7 g/d.kg $BW^{0.75}$, and 0.50 MJ/d.kg $BW^{0.75}$ and 10.8 g/d.kg $BW^{0.75}$, respectively. Milk protein ranged from 3.06 to 3.5% and milk fat averaged 5.2%. Glucose metabolism in Etawah crossbred female goat is active, but glucose flux is low compared to temperate ruminant breeds which may implicate its role to support production.

• Asian-Australasian Journal of Animal Sciences
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• 제15권9호
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• pp.1257-1262
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• 2002

The objective was to identify the appropriate form of progesterone, which exhibits compact reproductive responses in Awassi ewes during mid to late seasonal anestrous period. Forty-eight Awassi ewes were randomly allocated into four groups to be treated with 60 mg medroxyprogesterone acetate (MAP), 30 mg fluorogestone acetate (FGA), 40 mg FGA, or 600 mg progesterone sponges. After a 12 day period, sponges were removed and ewes were administered i.m. with 600 IU PMSG (d 0, 0 h). Five harnessed Awassi rams were turned-in with the ewes to detect heat. Ewes were checked for breeding marks at 6 h intervals for 5 days. Blood samples were collected from all ewes for analysis of progesterone concentrations. Pretreatment (d -13 and -12) progesterone concentrations were ${\leq}0.2ng/mL$ among all ewes and were indicative of seasonal anestrous period. On d 0, progesterone concentrations were elevated to $1.4{\pm}0.1ng/mL$ in ewes received progesterone sponges only and were higher (p<0.0001) than those (${\leq}0.2ng/mL$) administered MAP or FGA sponges. Progesterone concentrations returned to their basal values of <0.2 ng/mL within 24 h of sponge removal and were similar (p>0.1) among all ewes. Incidence of estrus was similar (p>0.1) among the four groups and occurred in 75% (9/12), 82% (9/11), 67% (8/12) and 58% (7/12) of the ewes receiving MAP, 30 mg FGA, 40 mg FGA and progesterone sponges, respectively. Estrous responses occurred 14.7, 20 and 13.6 h earlier in progesterone-sponge-treated ewes than those of MAP- (p<0.04), 30 mg FGA- (p<0.01) and 40 mg FGA-treated (p=0.06) ewes, respectively. Induced estrus conception rates were 50% (6/12), 55% (6/11), 50% (6/12) and 42% (5/12), out of which 4/6, 4/6, 3/6 and 3/5 lambed 151 days following d 0, and were similar (p>0.1) among ewes of the four treatment groups. Ewes that returned to estrus 16 to 20 days following d 0 were 5/12, 5/11, 6/12 and 4/12 ewes treated with MAP, 30 mg FGA, 40 mg FGA and progesterone sponges, respectively, and all lambed 169 days later. Overall lambing rates were 75% (9/12), 82% (9/11), 75% (9/12) and 58% (7/12) ewes treated with MAP, 30 mg FGA, 40 mg FGA and progesterone sponges, respectively. Results demonstrate that applications of MAP, 30 mg FGA, 40 mg FGA and progesterone sponges Awassi ewes were equally effective in induction of estrus and tended to favor both types of FGA and MAP in overall lambing rates over progesterone sponges during the seasonal anestrous period.

• 한국재료학회지
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• 제21권5호
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• pp.277-282
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• 2011

Negative temperature coefficient (NTC) materials have been widely studied for industrial applications, such as sensors and temperature compensation devices. NTC thermistor thick films of $Ni_{1+x}Mn_{2-x}O_{4+{\delta}}$ (x = 0.05, 0, -0.05) were fabricated on a glass substrate using the aerosol deposition method at room temperature. Resistance verse temperature (R-T) characteristics of the as-deposited films showed that the B constant ranged from 3900 to 4200 K between $25^{\circ}C$ and $85^{\circ}C$ without heat treatment. When the film was annealed at $600^{\circ}C$ 1h, the resistivity of the film gradually decreased due to crystallization and grain growth. The resistivity and the activation energy of films annealed at $600^{\circ}C$ for 1 h were 5.203, 5.95, and 4.772 $K{\Omega}{\cdot}cm$ and 351, 326, and 299 meV for $Ni_{0.95}Mn_{2.05}O_{4+{\delta}}$, $NiMn_2O_4$, and $Ni_{1.05}Mn_{1.95}O_{4+{\delta}}$, respectively. The annealing process induced insulating $Mn_2O_3$ in the Ni deficient $Ni_{0.95}Mn_{2.05}O_{4+{\delta}}$ composition resulting in large resistivity and activation energy. Meanwhile, excess Ni in $Ni_{1.05}Mn_{1.95}O_{4+{\delta}}$ suppressed the abnormal grain growth and changed $Mn^{3+}$ to $Mn^{4+}$, giving lower resistivity and activation energy.

• 공업화학
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• 제8권6호
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• pp.954-959
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• 1997

$Sr_{1-X}M_XFeO_{3-y}$ 계에서 (M=Ca), x=0.1, 0.2, 0.3, 0.4, 0.5에 대응하는 페로브스카이드계 고용체를 공기중, 1473K에 18시간 동안 열처리하여 합성하였다. X-선회절분석 결과 모든 고용체는 단순 입방정계를 나타내며, x=0.3까지는 x값의 증가에 따라 단위세포의 부피가 감소하고, x=0.4 이후에는 급격히 증가한다. 모어염 분석에 의하여 각각의 조성에 대한 $Fe^{4-}$ 이온의 몰비($\tau$값), 산소공위의 양(y값) 및 비화학양론적 화학식을 결정하였다. TG/DTA 실험(온도범위:300~1173K) 결과 x=0.1, 0.2인 시료는 3-y값이 감소하며, 냉각시 3-y값이 거의 가역적인 증가 경향을 보였다. $x{\geq}0.3$인 시료는 가역적인 무게의 변화를 보이지 않았으며, 냉각과정에서 3-y값은 거의 2.5를 유지하였다. 상대적으로 낮은 온도범위에서 모든 시료의 전기전도도 값은 반도성 범위에서 변화하였다. 그리고 일정한 온도에서의 전도도는 x값의 증가에 따라 감소하였다. 본 훼라이트 계의 전도도 메카니즘은 혼합원자가 상태 사이의 전도성 전자의 건너뜀 모형으로 제안할 수 있을 것이다. 고온에서 각 시료의 전도성은 금속성으로 변화하였다.

• 한국수소및신에너지학회논문집
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• 제27권5호
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• pp.517-525
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• 2016

The present work investigates the effect of $K_2CO_3$ catalyst on steam gasification of Kideco coal and the deactivation of the catalyst due to thermal exposure and interaction with coal ash. The gasification reactivity at $700^{\circ}C$ is highly enhanced by $K_2CO_3$, which is not deactivated by the heat treatment at $T{\leq}800^{\circ}C$. TGA and XRD results prove minor decomposition of $K_2CO_3$ after the calcination at $800^{\circ}C$. $K_2CO_3$ is, however, evaporated at the higher temperature. Assuming the conversion of $K_2CO_3$ into $K_2O$ by the decomposition and into $K_2O{\cdot}2.5SiO_2$ and $KAlO_2$ by the interaction with coal ash, the reactivity of the gasification is evaluated in the presence of $K_2O$, $K_2O{\cdot}2.5SiO_2$ and $KAlO_2$. Among them, $K_2O$ is the most active, but much lower in the activity than $K_2CO_3$. XRD results show that $K_2CO_3$ could react readily with the ash above $700^{\circ}C$.

• 한국식품과학회지
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• 제14권3호
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• pp.197-202
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• 1982

인삼제품제조용(人蔘製品製造用)엑기스의 숙성중(熟成中)에 일어나는 ginsenosides의 분해(分解)에 미치는 온도(溫度)의 영향(影響)을 구명(究明)하기 위하여 숙성온도(熟成溫度) 및 시간(時間)에 따른 ginsenosides의 함량변화(含量變化)로써 분해속도상수(分解速度常數) 및 반감기(牛減期)를 구(求)하였고 분해속도상수(分解速度常數)와 온도(溫度)에 대(對)한 Arrhenius plot에 의하여 활성화(活性化)에너지 및 $Q_{10}$ value를 구(求)하여 ginsenosides의 분해속도상수(分解速度常數)의 온도의존성(溫度依存性)에 대(對)한 관계식(關係式)을 설정(設定)하였다. 가. ginsenosides의 분해반응(分解反應)은 1차반응(次反應)을 나타냈으며 분해시(分解時)의 반감기(半減期)가 $100^{\circ}C$에서 34시간(時間), $90^{\circ}C$에서 70시간(時間), $80^{\circ}C$에서는 131시간(時間)이므로 ginsenosides의 함량변화(含量變化)만을 고려(考慮)한다면 $80^{\circ}C$이하(以下)의$70^{\circ}C$ 부근에서 숙성(熟成)함이 바람직하다. 나. 숙성중(熟成中)에 ginsenoside-Re가 감소(減少)하는 대신 $ginsenoside-Rg_2$가 증가(增加)하고 $ginsenoside-Rg_1$이 감소(減少)하는 대신 $ginsenoside-Rh_1$이 증가(增加)하므로 ginsenosides의 상호변환관계(相互變換關係)가 인정(認定)되었다. 다. ginsenosides의 분해시(分解時)의 온도상화(速度常數)가 $80^{\circ}C$에서 $5.30{\times}10^{-3}\;hr^{-1}$, $90^{\circ}C$에서 $9.90{\times}10^{-3}\;hr^{-1}$, 100"C에서는 $20.50{\times}10^{-3}\;hr^{-1}$으로서 숙성온도(熟成溫度)가 $10^{\circ}C$높아질 때마다 분해속도상수(分解速度常數)가 약(約) 2배(培) 증가(增加)하였고 또 $Q_{10}$ value도 $2.01{\sim}3.49$로서 숙성온도(熟成溫度)가 높아질수록 ginsenosides는 상대적(相對的)으로 불안정(不安定)하였다. 라. ginsenosides분해시(分解時)의 활성화(活性化)에너지 ($E_a$)는 $16.8{\sim}30.1$ kcal/mole의 범위 안에 있으며 ginsenoside-Re 및 $-Rg_1$이 $ginsenoside-Rb_1,\;-Rb_2$, -Rc 및 -Rd 보다 훨씬 높으므로 troil saponin이 diol saponin보다 온도(溫度)의 영향(影響)을 더 많이 받고 있었다. 마. total ginsenosides의 분해반응시(分解反應時)의 활성화(活性化)에너지($E_a$)는 17.7kcal/mole이었고 분해속도상수(分解速度常數)의 온도의존성(溫度依存性)은 $k=4.574{\times}10^8{\exp}(-8898.8/T)$의 관계식(關係式)으로 표시(表示)할 수 있다

• 보존과학회지
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• 제31권1호
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• pp.21-27
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• 2015

국보 제193호 봉수형유리병은 5세기에 조성된 것으로 알려진 황남대총 남분의 수많은 부장품들 사이에 독특한 형태의 녹색 유리 편들로 심하게 파손된 채 출토되었다. 1984년 국립중앙박물관 보존과학실에서 본격적으로 보존처리를 실시하여 박물관에서 오랜 기간 동안 전시되어 왔지만, 30년이라는 세월로 인해 기존에 사용한 접착제는 심하게 열화가 되어 매우 불안전한 상태가 되었으며 특히 복원제로 사용한 에폭시 수지가 빛과 열에 의해 심하게 황변이 되어 더 이상 유물의 안정한 전시와 효과적인 전시가 이루어질 수 없어 이번에 재 보존처리를 하게 되었다. 이번 연구에서는 그동안 연구가 전혀 진행되지 않았던 세 조각으로 파손된 봉수형유리병 손잡이 부분을 금사로 정성스럽게 감아 수리에 사용한 3 조각의 금사를 중점적으로 살펴보았다. 금사에 대한 분석방법으로는 SEM-EDS와 Stereo Microscope를 사용하여 비파괴적으로 분석하였다. 먼저, SEM-EDS 분석 결과, Au 91.9wt%-Au 92.8wt% 와 Ag 5.9wt.%-Ag 6.5wt.%으로 Au 과 Ag의 합금인 금제로 밝혀졌다. 다음으로 광학현미경으로 금사의 제작기법을 관찰한 결과, 일반적으로 금사는 덩이 금을 두드려서 만들거나 구멍에 밀어 넣어 뽑아내는 인발 가공 또는 금판을 꼬아서 제작하는 방법으로 제작하는데 봉수형유리병 손잡이에서 분리한 금사는 표면에서 꼬임 흔적은 전혀 나타나지 않고 단지 길이 방향으로 미세한 줄무늬가 관찰되고 단면이 모두 채워진 상태인 것으로 보아 인발 가공하여 만든 것을 사용하여 보수한 것으로 생각된다. 이러한 분석 결과는 그동안 금사에 대한 연구가 대부분 금제품 유물의 구성품으로만 인식된 채 별도의 유물로 주목받지 못해 금사에 대한 제작기법에 대한 체계적인 연구가 매우 미흡한 편이기 때문으로 장차 금사에 대한 추가적인 연구가 진행된다면 이번 봉수형유리병 손잡이 고정에 사용된 금사 분석 결과가 기존 신라시대 금제 유물의 금사와의 상호 연관성을 밝혀내는데 좋은 자료가 될 것으로 생각된다.

• 한국수소및신에너지학회논문집
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• 제17권4호
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• pp.379-388
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• 2006

Two mesophilic trickling bed bioreactors filled with two different types of media, hydrophilic- and hydrophobic-cubes, were designed and conducted for hydrogen production under the anaerobic fermentation of sucrose. Each bioreactor consisted of the column packed with polymeric cubes and inoculated with heat-treated sludge obtained from anaerobic digestion tank. A defined medium containing sucrose was fed by the different hydraulic retention time(HRT), and recycle rate. Hydrogen concentrations in gas-phase were constant, averaging 40% of biogas throughout the operation. Hydrogen production rate was increased till $10.5\;L{\cdot}h^{-1}{\cdot}L^{-1}$ of bioreactor when influent sucrose concentrations and recycle rates were varied. At the same time, the hydrogen production rate with hydrophobic media application was higher than its hydrophilic media application. No methane was detected when the reactor was under a normal operation. The major fermentation by-products in the liquid effluent of the both trickling biofilters were acetate, butyrate and lactate. In order to run in the long term operation of both reactor filled with hydrophilic and hydrophobic media, biofilm accumulation on hydrophilic media and biogas produced should be controlled through some process such as periodical backwashing or gas-purging. Four sample were collected from each reactor on the opposite hydrogen production rate, and their bacterial communities were compared by terminal restriction fragment length polymorphism (T-RFLP) analysis of PCR products generated using bacterial 16s rRNA gene primers (8f and 926r). It was expressed a marked difference in bacterial communities of both reactors. The trickling bed bioreactor with hydrophobic media demonstrates the feasibility of the process to produce hydrogen gas. A likely application of this reactor technology can be hydrogen gas recovery from pre-treatment of high carbohydrate-containing wastewaters.