• Proceedings of the Korean Fiber Society Conference
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• 1990.06b
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• pp.36-37
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• 1990

In the past, facile dissolution of cellulose has been hampered by the lack of suitable nondegrading solvents. Recently, this problem has been solved in our laboratory by the discovery of an inexpensive, convenient solvent system, that is the mixture of $NH_3\;and\;NH_4SCN$, for cellulose. Also, the $cellulose/NH_3/NH_4SCN$ solution system has been found to form the anisotropic, i.e., liquid crystalline phase. It is believed that both the cholesterio and the nematic phase occur. This finding has prompted extensive on-going researoh on the formation of the liquid crystalline phase from an inexpensive natural source such as cellulose since the nematic phase is envisioned as an excellent precursor sources for products with desirable properties, for example, high modulus and high strength. This interest naturally leads to a desire to understand the theological properties of the nematic phase so that the transformation of the nematic phase to the solid state with desirable properties can be efficiently accomplished, ;From this point of view, the theological behavior of the $cellulose/NH3_/NH_4SCN$ system has been studied as a function of shear rate and shear stress over a wide range of solvent compositions, cellulose concentration, centrifugation and urea contents, Results indicate that the viscosity decreases with increasing shear rate. A marked shear thinning behavior and a quasi-Newtonian behavior were observed in the low shear rate region and in the high shear rate region, respectively for all solvent compositions. The $cellulose/NH_3/NH_4SCN$ solution system only exhibited the viscosity increase with increasing cellulose concentration and failed to show the viscosity drop generally observed at the point of incipience of liquid crystal formation, This may be due to the gel-like nature of the solution by the association of the rodlike molecules into bundles which may serve as crosslinking points giving the cellulose solution a network structure. Also, simply hydrogen bonding may be so restrictive of molecular mobility that a viscosity drop is blocked. In addition to the above results, yield stress and thixotropy were also observed in the $cellulose/NH_3/NB_4SCN$ solution system which are characteristics of liquid crystal and gel, The results of the effect of centrifugation on viscosity show that viscosity decreases by the application of centrifugation. This may be explained by the change of the piled polydomain structure to the dispersed polydomain structure due to the pressure gradient generated during centrifugation.ation.

• Journal of Microbiology and Biotechnology
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• v.9 no.4
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• pp.522-524
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• 1999

A discontinuous Percoll gradient was used to separate islets from the collagenase-treated mouse pancreas easily and rapidly. Since the osmolality of Percoll is very low, adjustment of its osmolality to 340 mOs/kg $H_2$O was essential for securing the optimal separation. A discontinuous gradient layering with Percoll solution of 1.09 g, 1.07g, and1.05g/m, respectively, when centrifuged at 800$\times$g for 10 min, resulted in an optimal condition for separation and yielded a banding pattern with an even distribution of islet cells. No significant difference was observed in the morphological features between the Percoll-isolated and the manually-isolated islets. In conclusion, the discontinuous Percoll gradient can be effectively used to isolate the pancreatic islets from mice with four-fold higher efficiency compared to the handpicking method.

• Microbiology and Biotechnology Letters
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• v.22 no.4
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• pp.436-442
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• 1994

The characteristics of activated sludge affecting the biodegradation of plastic materials under aerobic condition were studied using cellophane film as a model system. The activated sludges of site 3, which treat a mixture of domestic sewage and supernatant of septic tank, obtained from December 1993 to April 1994 showed similar biodegradation activities. Biodegradations for 28 days reached around 80%. Viable cell number of inoculums maintained at a level of 10$^{6}$~10$^{7}$ /ml. In this range, viable cell number showed no relationship with biodegradation activities. The activa- ted sludges of site 2, which treat a mixture of domestic sewage and anaerobic digest of nightsoil, obtained four times from April 1993 to April 1994 showed very different biodegradation activities ranged from 20% to 80% for 28 days. Inoculum size affects biodegradation significantly. One percent inoculum showed the best biodegradation among the inoculum sizes of 0.1, 1.0 and 10%. Ten percent inoculum revealed inhibitory effects on the biodegradation activity which can be greatly reduced by centrifugation and filtration. Filtration was better than centrifugation in reducing inhibitory effects.

• Journal of Microbiology and Biotechnology
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• v.3 no.3
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• pp.181-187
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• 1993

Steroid $\Delta^1$-dehydrogenase which introduces a double bond into the 1, 2 positions of steroid ring A was purified from Arthrobacter simplex, an excellent biotransformer of hydrocortisone into prednisolone. Hydrocortisone-induced cells were disrupted by vigorous agitation with glass beads, and a solubilized enzyme was obtained after centrifugation at 100, 000$\times$g for 90 minutes. The enzyme was purified 123-fold in three steps of chromatographic procedures with 13% yield. The last step of testosterone-agarose affinity column decisively contributed to the successful purification. The molecular weight of the enzyme was estimated to be 98, 000 by SDS-PAGE and 100, 000 by gel filtration, indicating that this enzyme behaves as a monomer. The enzyme showed demands for artificial electron acceptor, and among the several reagents tested, phenazine methosulfate acted as the most effective electron acceptor. Subcellular distribution of this enzyme was studied by centrifugation experiment. Comparison of the enzyme activities in pelleted membrane and cytosol fractions suggests that the enzyme may be a weakly attached peripheral membrane protein in vivo. But considerable amounts of enzyme was solubilized without any additional treatments for membrane protein.

• Journal of Korean Society on Water Environment
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• v.25 no.5
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• pp.727-734
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• 2009

This study was carried out to evaluate the high rate biological reactor such as lab scale reactor before the application in site, and to get the basic data for possibility using liquid fertilizer with the effluent from biological reactor when the centrifugal machine was applied. The total volume of this reactor in 6 L, in composted of anoxic reactor (2 L), aerobic reactor (2 L), and nitification reactor (2 L). BOD removal efficiency rates when centrifugal machine was applied after effluent from biological reactor are over than 95%. This biological reactor was required post process to satisfy the effluent standards, and was need centrifugal machine to control the washout of microbes in the reactor. T-N removal efficiency rate in HRT 24 hr with centrifugation is 80.0%, and it is desirable to operate less than $1.3kgN/m^3{\cdot}d$ for 70% of T-N removal efficiency rate. T-P removal efficiency rate in HRT 24 hr is 68.2%, and become higher 71.3% after centrifugation. Considering in the 28.6% T-N removal efficiency rate, the nitrogen contents of the effluent from reactor is 0.34% to satisfy the liquid fertilizer.

• The Journal of Korean Society of Virology
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• v.28 no.1
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• pp.21-30
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• 1998

Synthetic genes encoding the gag p24 and the part of the envelope protein gp41 of the human immunodeficiency virus (HIV-1) were cloned and overexpressed as fusion proteins in Escherichia coli, using an expression vector carrying T7 promoter and the poly-histidine leader, sequence. The overexpressed p24 fusion protein was purified by centrifugation, Ni-affinity chromatography and CM-sepharose chromatography. The overexpressed gp41 fusion protein was purified by centrifugation, $C_4$ chromatography and DEAE-sepharose chromatography. The purified fusion proteins showed a high level of purity and immunoreactivity in SDS-polyacrylamide gel electrophoresis and western blot analysis. These results suggest that this prokaryotic - expression purification method is suitable for obtaining a large amount of the viral antigen which may be useful for screening of antibodies to HIV-1 in human blood samples.

• Food Science and Biotechnology
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• v.15 no.2
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• pp.189-195
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• 2006

A study was conducted to develop optimal conditions for a large-scale, sequential separation method for value-added components from egg yolk. Starting with liquid egg yolk, immunoglobulin Y (IgY), phospholipids, and neutral lipids were extracted sequentially using water, ethanol, and n-hexane. The remainder was yolk proteins. Adjusting the pH of diluted egg yolk to pH 5.0-5.2 decreased phospholipids content in the supernatant after centrifugation, which was very important for preventing clogging problem of ultrafiltration filters during the subsequent concentration step for IgY separation. Extraction of precipitants after centrifugation with four volumes of 100% ethanol once removed most of the phospholipids and the purity of phospholipids was more than 85% (wt.) after drying. The subsequent extraction of precipitant from ethanol extraction with four volumes of hexane 3 times removed neutral lipids almost completely and resulted in a high protein product with minimal lipids. The sequential separation method is considered to be advantageous for large-scale separations of many valuable components from egg yolk.

• ALGAE
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• v.25 no.2
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• pp.99-104
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• 2010

A psychrotolerant cyanobacterium, Nodularia spumigena KNUA005, was isolated from a cyanobacterial bloom sample collected near Dasan Station in Ny-${\AA}lesund$, Svalbard Islands during the Arctic summer season. To generate an axenic culture, the isolate was subjected to three purification steps: centrifugation, antibiotic treatment and streaking. The broad antibacterial spectrum of imipenem killed a wide range of heterotrophic bacteria, while the cyanobacterium was capable of enduring both antibiotics, the remaining contaminants that survived after treatment with imipenem were eliminated by the application of an aminoglycoside antibiotic, kanamycin. Physical separation by centrifugation and streaking techniques also aided axenic culture production. According to the cold-tolerance test, this mat-forming cyanobacterium was able to proliferate at low temperatures ranging between 15 and $20^{\circ}C$ which indicates the presence of cold-tolerance related genes in N. spumigena KNUA005. This suggests the possibility of incorporating cold-resistance genes into indigenous cyanobacterial strains for the consistent production of algae-based biofuel during the low-temperature seasons. Therefore, it is needed to determine the cold-tolerance mechanisms in the Arctic cyanobacterium in the next research stage.

• Restorative Dentistry and Endodontics
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• v.16 no.1
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• pp.236-244
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• 1991

Numerous studies have been focused on the immunologic aspects of inflamed pulp and periapical tissues. The purpose of this study was to evaluate levels of serum IgG and IgM in patients of acute pulpitis and acute apical abscess using Enzyme-Linked Immunosorbent Assay. Streptococcus mutans, Streptococcus sanguis, Bacteroides intermedius and Bacteroides gingivalis were grown for use as antigen and they were harvested by centrifugation. The patients were divided into 3 groups; patients of acute apical abecess, acute pulpitis and normal control 5 patients of each group were selected and their blood was obtained via intravenous puncture. Sera were prepared by centrifugation of each blood samples. Then serum antibodies were measured by modified ELISA. The following results were obtained; 1. Serum IgM levels of patients with acute pulpitis and acute apical abscess seemed to be slightly higher than those of normal control 2. Serum IgG levels of patients with acute apical abscess were slightly higher than those of normal control 3. Serum IgG and IgM levels of acute apical abscess patients and serum IgM levels of acute pulpitis were highest to Bacteroides gingivalis.

• BMB Reports
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• v.29 no.6
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• pp.540-544
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• 1996

Ferritins from germinated pumpkin seeds were isolated by ammonium sulfate precipitation (0.55 saturation), ion-exchange chromatography on DEAE-cellulose, and gel filtration chromatographies on Sephacryl S-300 and Sephadex G-100. Pumpkin ferritin contains less iron than soybean ferritin. Pumpkin ferritin cross-reacted with anti-soybean ferritin antiserum made in rabbit, and showed two distinct antibody reactive bands, both of equal intensity. The pumpkin ferritins corresponding to the two bands were separable by centrifugation in a sucrose gradient (20~50%). The molecular weights of the native pumpkin ferritins based on the estimation of sucrose gradient centrifugation, gel filtration on Sephacryl S-300 and non-denaturing polyacrylamide gel electrophoresis appeared to be: 530~580 KD (the large molecular weight pumpkin ferritin) and 330-360 KD (the small molecular weight pumpkin ferritin) The large molecular weight pumpkin ferritin contains less iron. Both pumpkin ferritins cross-reacted with anti-soybean ferritin antibody with a spur formation suggesting partial antigenic recognition.