• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.6
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• pp.335-339
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• 2002

Laboratory experiments were conducted using pure cultures of Acinetobacter under an-aerobic/aerobic cyclic conditions to explain the release and uptake of soluble phosphate in an activated sludge process showing enhanced biological phosphate removal (EBPR). Under anaerobic/aerobic cyclic conditions in a Sequencing Batch Reactor (SBR), COD uptake concurrent with soluble phosphate release by Acinetobacter was not significant during the anaerobic periods, indicating that EBPR would not be established in pure cultures. However Acinetobacter cells accumulated higher phosphate content (5.2%) in SBR than that obtained (4.3%) from batch experiments. These results suggest that Acinetobacter sp. may not follow the proposed pattern of behavior of poly-P bacteria in EBPR activated sludge Plants.

• Bulletin of the Korean Chemical Society
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• v.14 no.2
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• pp.292-294
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• 1993

Three derivatives of poly(ethylenimine) (PEI) are prepared by Ni(II)-template condensation with glyoxal(GO): PEI[Ni(II)-GO]$_{0.08}$ (1), PEI[Ni(II)-GO]$_{0.03}$ (2), and lau$_{0.18}$PEI[Ni(II)-GO]$_{0.03}$ (3). The contents of Ni(II)-macrocyclic center of 1-3 are 8%, 3%, or 3%, respectively, of the monomer residues, and 18% of monomer residues for 3 are laurylated. The pH profiles for k$_{cal}$ and k$_m$ for the deacylation of 4-carboxy-2-nitrophenyl acetate are measured. The relative magnitude of the parameters for 1-3 and different shapes of the pH profiles for 1-3 are explained in terms of the electrostatic and the hydrophobic effects exerted by the metal centers and lauryl groups. For the artificial metalloenzymes built on PEI, therefore, the ionization of functional groups and the affinity toward counter-anions can be controlled by adjusting charge density and the content of hydrophobic groups.

• KSBB Journal
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• v.10 no.5
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• pp.533-539
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• 1995

An autolytic system based on a thermally inducible phage lambda, λHL1, has been applied for the recovery of poly(3-hydroxybutyrate) [PHB] from a recombinant Escherichia coli XL1-Blue, harbouring a plasmid (pSYL105) containing the Alcaligenes eutrophus PHB biosynthesis genes. The lytic capability ofλHL1 was evaluated in flask culture for both lysogens, XL1-Blue (λHL1) and XL1-Blue (λHL1, pSYL105). When the optical density of culture at 600nm(OD600) reached 0.2, cell lysis was induced by increasing the temperature from $30^{\circ}C$ to $42^{\circ}C$. Most cells of XL1-Blue ($\lambda$HL1) were lysed by the autolytic system in an hour after the thermal induction, while the lytic efficiency was slightly lower for XLl-Blue (λHL1, pSYL105). The existence of pSYL105 in cells seemed to inhibit, to some extent, the lytic capability of λHL1 even at low PHB content. The lylic efficiency remarkably decreased as the induction was delayed to allow PHB accumulation. When a chemical induction using 2% (v/v) chloroform was introduced after an hours of thermal induction, we could obtain a good lytic efficiency.

• Macromolecular Research
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• v.11 no.6
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• pp.410-417
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• 2003

Poly(methyl methacrylate-co-acrylonitrile) [P(MMA-co-AN)]/Na-MMT nanocomposites were synthesized through emulsion polymerization with pristine Na-MMT. The nanocomposites were exfoliated up to 20 wt% content of pristine Na-MMT relative to the amount of MMA and AN, and exhibited enhanced storage moduli, E', relative to the neat copolymer. The exfoliated morphology of the nanocomposite was confirmed by XRD and TEM. 2-Acryla-mido-2-methyl-1-propane sulfonic acid (AMPS) widened the galleries between the clay layers before polymerization and facilitated the comonomers, penetration into the clay to create the exfoliated nanocomposites. The onset of the thermal decomposition of the nanocomposites shifted to a higher temperature as the clay content increased. By calculating areas of tan$\delta$ of the nanocomposites, we observed that the nanocomposites show more solid-like behavior as the clay content increases. The dynamic storage modulus and complex viscosity increased with clay content. The complex viscosity showed shear-thinning behavior as the clay content increased. The Young's moduli of the nano-composites are higher than that of the neat copolymer and they increase steadily as the silicate content increases, as a result of the exfoliated structure at high clay content.

• Journal of the Korean Chemical Society
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• v.39 no.5
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• pp.421-426
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• 1995

The hydrogels of hydrophilic three-dimensional methacrylate polymer networks were prepared from 2-hydroxyethyl methacrylate (HEMA) and ethylene glycol dimethacrylate (EDGMA) in aqueous solution. The interaction of water with the hydrophilic methacrylate polymers in the hydrogels was studied by pulse NMR spectroscopy. The spin-lattice relaxation times (T1) of low water content hydrogels showed the different double environments, resulting in two spin-lattice relaxation times (T1a and T1b). The values of T1a and T1b were 16.4${\times}$10-3 sec and 58.2${\times}$10-3 sec for a p(HEMA)-(10% H2O) system, and 13.2${\times}$10-3 sec and 23.1${\times}$10-3 sec for a crosslinked EGDMA-p(HEMA)-(10% H2O) system, respectively. The spin-spin relaxation times (T2) of the hydrogels were also measured as a function of water content in the p(HEMA)-(H2O)n and crosslinked EGDMA-p(HEMA)-(H2O)n system. The values of T2 were approximately 10 times less than those of T1 in agreement with the principles of spin relaxations.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.10
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• pp.992-998
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• 2008

Recently, a new concept for nitrogen removal that is simultaneous nitrification and denitrification(SND) has been studied for wastewater treatment process. The DMR(Daiho Microbic Revolution) process that used in this study consists of two suspended anoxic, anaerobic reactors and an aerobic biofilm reactor. The function of aerobic environment and the intensity of air flow rate(2.0, 1.0, 0.5, 0.4, 0.2 L/min) were studied in the biofilm reactor; also SND and nutrient removal efficiencies were investigated. Experimental results indicated that the change in air flow did not affect COD$_{Cr}$ removal significantly. Thus sustained at 93%. The lower the air flow rate, the higher T-N removal efficiency was attained(i.e.80% at 0.2 L/min). SND efficiency was 62, 65, 72 and 78% corresponding to each air flow rate. T-P removal was sensitive to aeration intensity and removal enhanced from 75% to 96% when the air flow rate was changed from 2.0 to 0.5 L/m; however second release occured in the clarifier at 0.2 L/min. Phosphorus content of activated sludge was 5.0%, as P releases and acetate uptake a ratio of 0.75 mg P/ mg HAc.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.767-771
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• 1999

Poly(ester-imide)(PEI) for the electrical insulation coating was synthesized and evaluated with one-step method as well as two-step method. For the synthesis of poly(ester-imide), imide repeat unit of N,N'-(4,4'-diphenylmethane) bistrimellitimide(DID) was initially made from trimellitic anhydride(TMA) and methylene dianiline(MDA), followed by the second stage reaction of esterification. One-step reaction was performed by reaction of TMA, MDA, dimethyl terephthalate(DMT), ethylene glycol(EG), and 1,3,5-tris-(2-hydroxy ethyl) isocyanurate(THEIC) in m-cresol solvent at a time. The synthesized poly(ester-imide) was cured with xylene, P-5030K(phenol-formaldehyde resin), TK-8(TDI type blocked polyisocyanate) and tetrapropyltitanate(TPT). It was found that the content of hydroxyl group, amount of DMT, and imide repeat unit played important role for the properties of electrical insulation coating film.

• KSBB Journal
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• v.14 no.1
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• pp.58-65
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• 1999

A hydrogel, poly(N-isopropylacrylamide-co-N,N'-dimethylaminopropyl methacrylamide), sensitive to both pH and temperature was synthesized and characterized for its welling behavior, lower critical solution temperature (LCST), and its appearance. The hydrogel with 5 mol% of N,N'-diemthylaminopropyl methacrylamide (DMAPMAAm) increased its volume phenomenonally in a lower pH range (ph 1~8) even at temperature ($37^{\circ}C$ and $40^{\circ}C$) higher than LCST. This behavior was unique compared to the temperature -sensitive hydrogel which did not exhibit any swelling in the same pH range. The hydrogel with 20 mol% of DMAPMAAm was swollen significantly at a higher pH of 12. With pH decrease from 12 to 2 water content in the gel increased from 38.8 wt% and 60.6 wt%, and 90.8 wt% for 5 mol% and 20 mol% gel, respectively. The transition pH that pH effect overwhelmed temperature effect occurred at a lower pH for a higher temperature ($40^{\circ}C$) and a lower mol% (5 mol%) of DMAPMAAm. Transparency and LCST of the gel increased with higher DMAPMAAm mol%.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.3
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• pp.255-261
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• 2006

This study was Conducted to investigate the effect of ${\gamma}-PGA\;({\gamma}-poly\;glutamic\;acid)$ on Ca absorption and bone metabolism in rats. Weaned 4-week old male rats were fed Ca-deficient diets for 3 weeks after the adjustment period. Rats were divided into 6 groups and were fed experimental diets for four weeks. Experimental groups were basal (Ca deficient), control (Ca diet: Ca 0.45%), CP1(Ca 0.45%+casein phosphopeptide 1%), PG1(Ca 0.45%+gamma poly glutamic acid 1%), CPG (Ca 0.45%+casein phosphopeptide 1%+gamma poly glutamic acid 1%) and PG3(Ca 0.45%+gamma poly glutamic acid 3%). Though daily Ca intake and food intake of experimental groups showed no significant difference that of control group. The values of fecal Ca excretion and urinary Ca excretion in groups fed ${\gamma}-PGA$ were significantly lower than that in tile control group. The values of Ca absorption in groups fed ${\gamma}-PGA$ were significantly higher than that in the control group. The levels of femur Ca in ${\gamma}-PGA$ supplemented group were significantly increased compared to the control group. Also, breaking force of femur in ${\gamma}-PGA$ supplemented group showed about 40% increase compared to the control group. These results show that ${\gamma}-PGA$ supplement could be helpful to increase Ca absorption as well as to intensify the femur strength and to increase the Ca content of femur in rats.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.735-738
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• 2001

Metabolically engineered Escherichia coli strains harboring a plasmid containing a novel artificial polyhydroxyalkanoate (PHA) operon consisting of the Aeromonas PHA biosynthesis related genes and Ralstonia eutropha reductase gene were developed for the production of poly(3-hydroxybutyrate-co-hydroxyhexanoate) [P(3HB-co-3HHx)] from dodecanoic acid. By applying stepwise reduction of dissolved oxygen concentration (DOC) during the fermentation, the final dry cell weight, PHA concentration, and PHA content of 79 g/L, 21.5 g/L, and 27.2 wt%, respectively, were obtained in 40.8 h, which resulted in the PHA productivity of 0.53 g/L/h. The 3HHx fraction slowly increased during the fed-batch culture to reach a final value of 10.8 mol%. The 3HHx fraction in the copolymer could be increased by three fold when the Aeromonas hydrophila orfl gene was co-expressed with the PHA biosynthesis genes.