• Applied Chemistry for Engineering
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• v.21 no.6
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• pp.659-663
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• 2010

Microalgae has been seen all over the seawater and several species are used for human food. Specially, Nannochloropsis oculata, a photosynthetic microalgae, has been focused for a vast array of valuable nutritious compounds. In order to find high mass Nannochloropsis oculata culture conditions, some of important growth factors of pH, temperature, culture media, and $CO_2$ effect were tested. The optimal growth condition was found to be as follows : 3% artificial seawater, initial pH 8.5, and temperature $25^{\circ}C$. The alga mass and chlorophyll content were dramatically increased by applying 5% flue $CO_2$ gas (1.50 g/L algae in a continuous $CO_2$ flue; 0.76 g/L alga without $CO_2$). It was shown that the chlorophyll biosynthesis was also closely associated with alga growth.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.385-388
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• 2003

폐광석에 함유되어 있는 총중금속함량을 측정하기 위한 전함량분석과 중금속을 다량 함유한 폐광석이 산성환경에 노출되어 있을 경우 중금속의 지화학적 거동을 파악하기 위해 산도를 변화시키면서 용출실험을 실시하였다. 전함량분석과 용출실험을 종합한 결과, 중금속 및 미량원소의 용출거동 특성을 크게 As-Co-Fe 형태와 Cu-Mn-Cd-Zn형태와 Pb로 구분할 수 있었다. As-Co-Fe의 용출특성은 약산성의 환경에서는 용출이 미약하나, 최종 pH 1.5이하의 강산성환경에서는 용출량이 급격하게 증가하며, Cu-Mn-Cd-Zn형태에서는 최초로 용해되는 pH가 5.0-3.0으로 As-Co-Fe 보다 다소 높았다. Pb는 다른 형태에 비해 상당히 적게 용출되었다 최종 용출된 함량과 관계없이 초기 용출이 발생하는 pH값을 기준으로 한 각 원소의 상대적인 이동성은 Mn =Zn>Cd=Cu>>Fe=Co>As>Pb 순서이며, 산성비는 Zn, Mn 및 Cu를 쉽게 용출시켜 이동도를 증가시킬 것으로 판단된다.

• Korean Journal of Microbiology
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• v.48 no.3
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• pp.200-206
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• 2012

A bacterial strain capable of synthesizing polyhydroxyalkanoates (PHAs) with an unusual pattern of monomer units was isolated from activated sludge using the enrichment culture technique. The organism, identified as Pseudomonas aeruginosa P-5, produced polyesters consisting of 3-hydroxyvalerate and medium-chain-length (MCL) 3-hydroxyalkanoate monomer units when $C_{-odd}$ alkanoic acids such as nonanoic acid and heptanoic acid were fed as the sole carbon source. Solvent fractionation experiments using chloroform and hexane revealed that the 3-hydroxyalkanoate monomer units in these polyesters were copolymerized. The molar concentration of 3-hydroxyvalerate in the polyesters produced were significantly elevated up to 26 mol% by adding 1.0 g/L valeric acid as the cosubstrate. These copolyesters were sticky with low degrees of crystallinity. The PHA synthase genes were cloned, and the deduced amino acid sequences were determined. P. aeruginosa P-5 possessed genes encoding MCL-PHA synthases (PhaC1 and PhaC2) but lacked the short-chain-length PHA synthase gene, suggesting that the MCL-PHA synthases from P. aeruginosa P-5 are uniquely active for polymerizing (R)-3-hydroxyvaleryl-CoA as well as MCL (R)-3-hydroxyacyl-CoAs.

• Journal of the Korean Magnetics Society
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• v.10 no.5
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• pp.203-209
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• 2000

Top synthetic spin valves with structure Ta/NiFe/CoFe/Cu/CoFe(P 1)/Ru/CoFe(P2)/FeMn/Ta on Si (100) substrate with natural oxide were prepared by dc magnetron sputtering system. We have changed only the thickness in free layers and the thickness difference (Pl-P2) in two ferromagnetic layers separated by Ru, and investigated the effect of magnetic film thickness on interlayer coupling field in spin valve with synthetic antiferromagnet. According to the decrease of free layer thickness, interlayer coupling field was increased due to the magnetostatic coupling(orange peel coupling). In case of t$\_$P1/>t$\^$P2/, interlayer coupling field agreed well with the modified Neel model suggested in conventional spin valve structures by Kools et al. However, in case of t$\_$P1/>t$\^$P2/, it was found that the interlayer coupling field was not explained by the Modified Neel Model and was confirmed the necessity of further remodeling. The dependence of Cu thickness on the interlayer coupling field was investigated and 10 Oe of interlayer coupling field was obtained when the Cu thickness is 32 $\AA$.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1500-1506
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• 2011

Tyrosinase is a widespread enzyme with great promising capabilities. The Lineweaver-Burk plots of the catecholase reactions showed that the kinetics of mushroom tyrosinase (MT), activated by $Co^{2+}$ and $Zn^{2+}$ at different pHs (6, 7, 8 and 9) obeyed the non-essential activation mode. The binding of metal ions to the enzyme increases the maximum velocity of the enzyme due to an increase in the enzyme catalytic constant ($k_{cat}$). From the kinetic analysis, dissociation constants of the activator from the enzyme-metal ion complex ($K_a$) were obtained as $5{\times}10^4M^{-1}$ and $8.33{\times}10^3M^{-1}$ for $Co^{2+}$ and $Zn^{2+}$ at pH 9 and 6 respectively. The structural analysis of MT through circular dichroism (CD) and intensive fluorescence spectra revealed that the conformational stability of the enzyme in these pHs reaches its maximum value in the presence of each of the two metal ions.

• Korean Journal of Animal Reproduction
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• v.21 no.4
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• pp.345-353
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• 1997

Antioxidants and antioxidants with somatic cell co-culture, bovine oviduct epithelial cells(BOEC) and buffalo rat liver cells(BRLC), were studied as a mean of increasing the development and intracellular glutathione(GSH) concnetrations of bovine embryos derived from in vitro matured(IVM) and in vitro fertilized(IVF) oocytes. Cell numbers and intracellular GSH concentrations of blastocysts were also counted. The developmental rate beyond morula stages in CRlaa containing taurine(2.5mM), superoxide dismutase(SOD, 600U) and catalase(250U) were 1%, 75.0%, 64.8% and 62.3%, respectively. The developmental rate in antioxidant groups was significantly higher than in control(P<0.05). The intracellular GSH concentrations of blastocysts cultured in 0, 2.5mM taurine, 600U SOD and 250U catalase were 33.8pM, 39.3pM, 42.3pM and 54.8pM, respectively. This result indicated that the developmental rates and intracellular GSH concentrations of catalase group was significantly higher than any other groups(P<0.05). The developmental capacity in CRlaa plus various antioxidants co-cultured with BOEC were 55.3%(control), 74.1%(2.5mM taurine), 66.7%(600U SOD) and 70.7%(250U catalase) and in CRlaa plus various antioxidants co-cultured with BRLC in control, 2.5mM taurine, 600U SOD and 250U catalase were 63.8%, 75.5%, 71.0% and 73.5%, respectveily, the intracellular GSH concentrations of blastocyst embryos co-cultured with BOEC and BRLC in CRlaa with 0.25mM taurine, 600U SOD and 250U catalase were 73.4pM and 64.4pM, 79.9pM and 67.5pM, 82.3pM and 71.7pM, and 83.0pM and 80.0pM, respectively. Cell numbers of blastocysts were not difference in all experimental groups. These studies indicate that andtioxidants and antioxidant with somatic cell co-culture can increase the proportion of embryo that developed into morula and blastocysts, and the intracellular GSH concentrations of blastocyst embryos.

• The Korean Journal of Pesticide Science
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• v.7 no.2
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• pp.108-116
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• 2003

A series of new quinclorac family, herbicidal 3-phenyl-5-(3,7-dichloro-8-quinolinyl)-1,2,4-oxadiazole derivatives as substrate were synthesized and their growth inhibition activity $(pI_{50})$ against root and shoot of rice plant (Oryza sativa L.) and barnyard grass (Echinochloa crus-galli) were determined. And then comparative molecular field analysis (CoMFA) and molecular holographic quantitative structure- activity relationship (HQSAR) were compared in terms of their potential for predictiability. The statistical results were suggested that HQSAR based model had better predictability than CoMFA model. The selective factors to remove barnyard grass take electron withdrawing groups which can be created positive charge and steric bulky on the phenyl ring. Results revealed that the unknown 2,6-dichloro-substituent, U5 and 2,4,6-trichloro-substituent, U6(${\Delta}pI_{50}$=CoMFA: 1.18 & HQSAR: 1.82) were predicted as compound with higher activity and selectivity.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.12
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• pp.2163-2173
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• 2000

The optimum pH range for biosorption of cobalt by methanotrophic bacteria was broadened to 6.0~12.0 which was compared to pH 10.5~11.5 of bios or bent-free control case. Removal efficiency of cobalt by methanotrophic biomass was pH dependent, but less sensitive than that of control. With 1.0 g biosorbent/L at initial solution pH 6.0. methanotrophic biomass took up cobalt from aqueous solutions to the extent of 170 mg/g biomass. As a result of scanning electron microscope(SEM) micrographs, cobalt removal by methanotrophic biomass seemed to be through adsorption on the surface of methanotrophic biomass and by exopolymer around the biomass. Optimum amount of methanotrophic biomass for maximum cobalt uptake was 1.0 g/L for initial 400 mg Co/L at initial pH 6.0. Removal efficiency of cobalt was slightly affected by ionic strength up to 2.0 M of NaCl and $NaNO_3$, respectively.

• Journal of Microbiology and Biotechnology
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• v.34 no.5
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• pp.1119-1125
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• 2024

Phytase increases the availability of phosphate and trace elements by hydrolyzing the phosphomonoester bond in phytate present in animal feed. It is also an important enzyme from an environmental perspective because it not only promotes the growth of livestocks but also prevents phosphorus contamination released into the environment. Here we present a novel phytase derived from Turicimonas muris, TmPhy, which has distinctive structure and properties compared to other previously known phytases. TmPhy gene expressed in the Pichia system was confirmed to be 41 kDa in size and was used in purified form to evaluate optimal conditions for maximum activity. TmPhy has a dual optimum pH at pH3 and pH6.8 and exhibited the highest activity at 70℃. However, the heat tolerance of the wildtype was not satisfactory for feed application. Therefore, random mutation, disulfide bond introduction, and N-terminal mutation were performed to improve the thermostability of the TmPhy. Random mutation resulted in TmPhyM with about 45% improvement in stability at 60℃. Through further improvements, a total of three mutants were screened and their heat tolerance was evaluated. As a result, we obtained TmPhyMD1 with 46.5% residual activity, TmPhyMD2 with 74.1%, and TmPhyMD3 with 66.8% at 80℃ heat treatment without significant loss of or with increased activity.

• Journal of Pharmaceutical Investigation
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• v.40 no.4
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• pp.251-254
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• 2010

The formation of acylated peptide impurities in poly(lactide-co-glycolide) (PLGA) formulations is one of the major challenges to the development of successful sustained-release product. Octreotide, synthetic analogue of somatostatin, has been identified to be acylated in PLGA microsphere formulations. The purpose of this study was to investigate the pH effect on the formation of acylated octreotides by PLGA. In the incubation with PLGA in 0.1 M phosphate buffer at pH 7.4, approximately 98% of octreotide adsorbed to PLGA through 14 days and 66.3% of acylated octreotides were produced after 42 days, whereas the interaction of octreotide with PLGA was significantly inhibited in the incubation at pH 4, in which the acylated octreotides were observed to be 9.2% after 42 days. In the interaction study at pH 4.1-7.4, the production of acylated octreotides was demonstrated to be dependent on environmental pH. Below pH 5.0, the acylation of octreotide was significantly inhibited. This study indicates that the pH is the major factor for the formation of acylated octreotide in PLGA formulations.