• 한국토양비료학회지
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• 제49권1호
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• pp.17-29
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• 2016

Though there is an abundant supply of nitrogen in the atmosphere, it cannot be used directly by the biological systems since it has to be combined with the element hydrogen before their incorporation. This process of nitrogen fixation ($N_2$-fixation) may be accomplished either chemically or biologically. Between the two elements, biological nitrogen fixation (BNF) is a microbiological process that converts atmospheric di-nitrogen ($N_2$) into plant-usable form. In this review, the genetics and mechanism of nitrogen fixation including genes responsible for it, their types and role in BNF are discussed in detail. Nitrogen fixation in the different agricultural systems using different methods is discussed to understand the actual rather than the potential $N_2$-fixation procedure. The mechanism by which the diazotrophic bacteria improve plant growth apart from nitrogen fixation such as inhibition of plant ethylene synthesis, improvement of nutrient uptake, stress tolerance enhancement, solubilization of inorganic phosphate and mineralization of organic phosphate is also discussed. Role of diazotrophic bacteria in the enhancement of nitrogen fixation is also dealt with suitable examples. This mini review attempts to address the importance of diazotrophic bacteria in nitrogen fixation and plant growth improvement.

• Applied Biological Chemistry
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• 제48권3호
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• pp.189-200
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• 2005

생물학적 질소고정과정의 연구는 학문적으로나 산업적으로 매우 중요한 과정이다. 본 총설에서는 공업적 질소고정과 비교되는 생물학적 질소고정의 특징을 간단히 살펴보고, Azotobacter vinelandii에서 연구되고 있는 생물학적 질소고정효소의 특징을 다룬다. 생물학적 질소고정과정은 다양한 생명체에서 일어나며, 최근에는 미생물인 A. vinelandii에 그 작용 메커니즘에 관한 연구가 집중되어 있다. 공기중의 질소를 암모니아로 변환시키는 질소고정은 화학적으로 환원 반응에 해당하므로 전자의 공급이 필요하다. 생물학적 질소고정을 담당하는 질소고정효소는 촉매반응을 위해 생물학적인 환원력을 사용하여 전자를 공급받아, Fe 단백질의 $Fe_4S_4$ cluster와 MoFe 단백질의 P-cluster를 거쳐 질소 환원 반응이 일어나는 FeMo-cofactor로 전달한다. 이러한 전자전달의 과정과 수소이온의 전달 과정은 질소고정효소의 반응 메커니즘 이해에 매우 중요한 과정이며, FeMo-cofactor와 질소분자의 상호작용은 생물학적 질소고정 메커니즘의 중심에 있다. 질소고정 작용 메커니즘의 연구에는 X-선 단백질 결정학, EPR과 $M{\ddot{u}}ssbauer$ 등의 다양한 분광학적 방법과, 효소의 기질과 저해제의 상호작용을 연구하고 mutant와 비교하는 생화학적 접근방법, 그리고 FeMo-cofactor의 모델 화합물을 합성하여 연구하는 화학적 방법 등이 적용되었다. 이들 분야의 최근 연구결과를 소개하며, 마지막으로, 다양한 연구 결과에 바탕하여 새로운 질소고정효소의 작용 기작이 제안하였다.

• Fibers and Polymers
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• 제6권1호
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• pp.1-5
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• 2005

In this study, we attempted to evaluate a novel use of sericin-fixed silk fiber (SFx) as an immobilization support of enzyme. Sericin was fixed on the silk fiber using glutaraldehyde as a fixation reagent. After 6 hours of fixation, the degree of fixation increases linearly with linear decrease of the amount of bound $\alpha$-chymotrypsin (CT). This suggests that the increase of the degree of fixation is due to the further crosslinking of free aldehyde groups on the surface of sericin-fixed silk fiber (SFx). Even though perfect fixation was not achieved, sericin did not dissolve seriously and could be removed by further washing. The specific activity did not differ significantly after 6 hours of fixation. The activity of immobilized CT on SFx decreased to its half after 6 hours of incubation at 50$^{\circ}C$. However, it retained $78\%$ of initial activity even after 1 hour of treat­ment with $100\%$ ethanol. As a result, the SFx could be used as an immobilization support of enzyme in non-aqueous media at ambient temperature.

• Journal of Microbiology and Biotechnology
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• 제15권3호
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• pp.461-465
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• 2005

Characteristics of biological $CO_2$ fixation by Chlorella sp. HA-1 were investigated in a semi-continuous and series reactor system using an internally illuminated photobioreactor to overcome shortcomings of physicochemical technologies such as adsorption and membrane separation. High $CO_2$ fixation rate was achieved in the semi-continuous reactor system, in which the dilution ratios of the culture medium were controlled. The average $CO_2$ fixation rate was maintained almost constantly when the dilution ratio increased by 0.1 increment from the initial value of 0.5. The total removal efficiency of $CO_2$ was enhanced by employing a series reactor system. The average $CO_2$ fixation rate increased until 4.013 g $CO_2\;day^{-1}$ in a series operation of four reactors, compared to 0.986 g $CO_2\;day^{-1}$ in a batch operation mode. The total $CO_2$ fixation rate was proportional to the number of reactors used in the series reactor system. In the series reactor system of semi-continuous operation, a large amount of $CO_2$ was removed continuously for 30 days. These results showed that the present reactor systems are efficient and economically feasible for a biological $CO_2$ fixation.

• Biotechnology and Bioprocess Engineering:BBE
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• 제8권6호
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• pp.354-359
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• 2003

$CO_2$fixation by microalgae has emerged as a promising option for $CO_2$mitigation. In-tensive research work has been carried out to develop a feasible system for removing $CO_2$from industrial exhaust gases. However, there are still several challenging points to overcome in order to make the process more practical. In this paper, recent research activities on three key technologies of biological $CO_2$fixation, an identification of a suitable algal strain, development of high efficient photobioreactor and utilization of algal cells produced, are described. Finally the barriers, progress, and prospects of commercially developing a biological $CO_2$fixation process are summarized.

• KSBB Journal
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• 제15권6호
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• pp.644-648
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• 2000

Biological fixation of carbon dioxide using microalgae is known as an effective CO$_2$reduction technology. However, many environmental factors influence microalgal productivity. Optimal cultivation factors were determined for the green alga, Euglena gracilis Z, which offers high protein and vitamin E content for animal fodder. In batch culture in a photovioreactor, it was found that theinitial pH, temperature, CO$_2$concentration in air, and light intensity during the optimal cultivating conditions were 3.5, 27$^{\circ}C$, 5-10% and 520 ${\mu}$mol/㎡/s, respectively. When tap water and freshwater were used as cultivating media unsterilized tap water was found to be effective. A kinetic model was considered to determine the relationship between the specific growth rate and the light intensity. The half-velocity coefficient (K(sub)I) in the Monod model under photoautotrophic conditions was 978.9 ${\mu}$mol/㎡/s.

• Applied Microscopy
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• 제46권4호
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• pp.188-192
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• 2016

Proper sample preparation prior to microscopy is necessary for maintaining the components of tissues in a state as close to a living state as possible. For optimal preservation of biological samples, the sampling conditions are as important as the fixation itself. Various factors influence the selection and fixation efficiencies of a fixative, including sample size, osmolarity, pH, penetration rate and depth, fixative temperature, fixation time, fixative concentration, fixative amount, and retention time. Therefore, several factors for selecting and administering fixation procedures are evaluated pertaining to optimal sample preparation for transmission electron microscopy.

• KSBB Journal
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• 제18권4호
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• pp.340-345
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• 2003

본 연구에서는 대량으로 배출되는 이산화탄소를 고정화하기 위해서 lab 규모의 3 L 광생물 반응기(1)를 bench 규모의 40 L와 pilot 규모의 188 L로 스케일-업 했을 때 이산화탄소의 고정화 특성을 살펴보았다. 균체성장속도 즉, $CO_2$ 고정화 속도는 광생물 반응기가 스케일-업 됨에 따라 감소하였으며, 단위면적당 $CO_2$ 고정화 양은 40 L 광생물 반응기에서 530 g $CO_2$/$m^2$-day으로 가장 높았다. 반면, 총 $CO_2$ 고정화양은 반응기의 용량이 커짐에 따라 증가하였으며, 188 L 광생물 반응기에서 28.05 g $CO_2$/day를 얻었다. 광생물 반응기의 운전에 있어서 $CO_2$ 고정화속도의 향상은 단위면적당 $CO_2$ 고정화 양 및 총 $CO_2$ 고정화양을 증가시킨다. $CO_2$ 고정화속도에 영향을 미치는 운전인자 중에 가장 중요한 것은 광원으로 반응기의 스케일-업시 광원의 개수 및 배열을 조절함으로써 용량이 커짐에 따라 저감되는 $CO_2$ 고정화속도를 증가시킬 수 있었다. 또한 향후 스케일-업된 광생물 반응기에서의 물질전달 현상에 관한 연구를 동반함으로써 보다 높은 $CO_2$ 고정화속도를 얻을 수 있을 것으로 판단된다.

• 한국토양비료학회지
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• 제20권3호
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• pp.261-268
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• 1987

논상태(狀態)의 토양(土壤)에서 유기물(有機物)의 종류(種類), 질소비종(窒素肥種) 및 시비량(施肥量)을 달리했을 때 광합성(光合成) 및 타양성질소고정미생물(他養成窒素固定微生物)에 의한 생물학적(生物學的) 질소고정량(窒素固定量)과 Kjeldahl 분석(分析)에 의한 토양중(土壤中) 전질소함량(全窒素含量) 변화차이(變化差異)를 알고저 초자실(硝子室)에서 60일(日) 담수시험(湛水試驗)한 결과(結果)를 요약(要約)하면 다음과 같다. 1. 각종시용유기물중(各種施用有機物中) 탄소(炭素) 1mg당(當) 생물질소(生物窒素) 고정량(固定量)은 glucose 0.13mg, 볏짚 0.09mg, 그리고 양송이 폐상퇴비와 보리짚은 0.07mg이였다. 2. 토양종류(土壤種類)에 따른 질소고정량(窒素固定量)은 질소비종(窒素肥種)에 따라서 상이(相異)했으며 시비량(施肥量)이 증가(增加)할수록 감소(減少)했는데 감소(減少)의 정도(程度)는 유안(硫安)보다 요소시용시(尿素施用時) 현저(顯著)하였다. 3. 광조건별(光條件別) 질소비종(窒素肥種) 및 시비량(施肥量)에 따른 질소고정량(窒素固定量)은 사질토양(砂質土壤)에서 유안(硫安)이 요소(尿素)보다 증가(增加)되었으며 전질소고정량중(全窒素固定量中) 75%는 광합성미생물(光合成微生物)에 의하여 그리고 25%는 타양성질소고정미생물(他養性窒素固定微生物)에 의하여 고정(固定)되었다고 추정(推定)할 수 있었다. 그러나 식질토양(埴質土壤)에서는 광조건(光條件)과 질소비종간(窒素肥種間)에 뚜렷한 차이(差異)는 보이지 않했다. 4. 시험전후토양(試驗前後土壤)의 질소함량(窒素含量)을 보면 사질토양(砂質土壤)은 처리(處理)에 관계(關係)없이 시험후(試驗後) 토양(土壤)의 질소(窒素)가 현저(顯著)히 감소(減少)되었는데 그 정도(程度)는 요소시용구(尿素施用區)의 광차단조건(光遮斷條件)에서 현저(顯著)하였다. 한편 식질토양(埴質土壤)에서 비종간(肥種間)에는 큰차이(差異)를 볼 수 없었으나 광차단조건(光遮斷條件)에서 질소(窒素)의 감소(減少)가 현저(顯著)하였다. 5. Acetylene 환원법(還元法)에 의한 생물질소고정량(生物窒素固定量)과 Kjeldahl 분석(分析)에 의한 전질소함량변화차이(全窒素含量變化差異)는 평균(平均) 6:1의 비율(比率)을 보였다.

• Bulletin of the Korean Chemical Society
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• 제35권7호
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• pp.1970-1972
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• 2014

A facile and efficient synthesis of dronedarone hydrochloride starting from commercially available 4-nitrophenol is described. This approach features a tandem-type synthesis of 3-carbonylated benzofuran involving cyclization of 2-ethynylphenol followed by $CO_2$ fixation at the 3-position of the benzofuran ring mediated by potassium carbonate without the addition of any transition metal catalyst.