• KSBB Journal
• /
• v.21 no.5
• /
• pp.384-388
• /
• 2006

The production stability of high-yielding mutants of Streptomyces lincolnensis immobilized on celite beads was examined in repeated batch cultures. We also explored the feasibility of immobilization of vegetative mycelial cells on pre-wetted celite beads, which is practical method for cell immobilization. Repeated transfer of immobilized cells into fresh medium every 10 days increased productivity of immobilized cells and maximum concentration of lincomycin, 1007 $({\pm}256)$ mg/L, was obtained at the end of the ninth cycle. A 1.4-fold higher productivity was obtained in immobilized-cell culture than that obtained by suspended-cell culture. When pre-wetted beads were inoculated with vegetative mycelia and cultured a slightly higher amount of immobilized cells and lincomycin was obtained more than those obtained by culture of spores immobilized on dry beads. This result indicates that immobilization of mycelial cells on pre-wetted beads was readily available. This technique is simple and no additional facilities are required for cell immobilization.

• Applied Biological Chemistry
• /
• v.48 no.3
• /
• pp.189-200
• /
• 2005

Biological nitrogen fixation is an important process for academic and industrial aspects. This review will briefly compare industrial and biological nitrogen fixation and cover the characteristics of biological nitrogen fixation studied in Azotobacter vinelandii. Various organisms can carry out biological nitrogen fixation and recently the researches on the reaction mechanism were concentrated on the free-living microorganism, A. vinelandii. Nitrogen fixation, which transforms atmospheric $N_2$ into ammonia, is chemically a reduction reaction requiring electron donation. Nitrogenase, the biological nitrgen fixer, accepts electrons from biological electron donors, and transfers them to the active site, FeMo-cofactor, through $Fe_4S_4$ cluster in Fe protein and P-cluster in MoFe protein. The electron transport and the proton transport are very important processes in the nitrogenase catalysis to understand its reaction mechanism, and the interactions between FeMo-cofactor and nitrogen molecule are at the center of biological nitrogen fixation mechanism. Spectroscopic studies including protein X-ray crystallography, EPR and $M{\ddot{o}}ssbauer$, biochemical approaches including substrate and inhibitor interactions as well as site-directed mutation study, and chemical approach to synthesize the FeMo-cofactor model compounds were used for biological nitrogen fixation study. Recent research results from these area were presented, and finally, a new nitrogenase reaction mechanism will be proposed based on the various research results.

• KSBB Journal
• /
• v.18 no.5
• /
• pp.412-417
• /
• 2003

We first investigated basic characteristics of reticulated polyurethane (PU) foams as microbial carriers. In general, the specific surface area of PU foams increases with respect to decreasing pore sizes. However, the number of microbes adhered on the unit surface of reticulated PU foams decreases with respect to decreasing pore sizes. Thus, as a result of totally considering all effects such as apparent density, hydrolysis rate, and adhesion, we can know that PU foams with 45 PPI is the most appropriate microbial carrier. In this study, we can also investigate the effect of various physico-chemical surface treatments on the adhesion of microbes on the surface of PU foams. We used a chitosan treatment, a PEI (Polyethylene Imine) treatment, a xanthane treatment and a plasma treatment. As a result of comparing all surface treatments, the plasma surface treatment was the best.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.49 no.8
• /
• pp.73-81
• /
• 2012

In this paper, a novel phase locked loop has been proposed using an analog band-selection loop. When the PLL is out-lock, the PLL has a fasting locking characteristic with the analog band-selection loop. When the PLL is near in-lock, the bandwidth becomes narrow with the fine loop. A frequency voltage converter is introduced to improve a stability and a phase noise performance. The proposed PLL has been designed based on a 1.8V $0.18{\mu}m$ CMOS process and proved by HSPICE simulation.

• Microbiology and Biotechnology Letters
• /
• v.13 no.3
• /
• pp.251-255
• /
• 1985

Nitrogen-fixing bacteria were isolated from the rice rhizosphere of various paddy fields in our country. The screening of 235 isolates for nitrogen-fixing ability resulted in the isolation of Enterobacter agglomerans NFB264 and three Klebsiella pneumoniae NFB 3, NFB 320. Plasmids of various molecular weight from 1.7 to more than 84 Mal. were detected by agarose gel electrophoresis in three out of four isolates. But, these plasmids had not any nitrogen-fixing genes. Hybridization experiments using Klebsiella pneumoniae M5al nitrogen-fixing genes, nif Q-K and nif DH, as probes revealed the presence of homologous sequences in the chromosomal DNA of all isolates. However the restriction patterns of nif genes of the isolates by various restriction endonucleases were different to those of Klebsiella pneumoniae M5al.

• KSBB Journal
• /
• v.6 no.4
• /
• pp.403-406
• /
• 1991

Lactic acid production yield was examined for commercial use by immobilizing Rhizopus oryzae with radiation induced polymer. The supporting material was synthesized by the low temperature radiation polymerization method, in which the microorganism was entrapped physically by contacting together in culture broth shaking for 24 hours. Support polymers with 5∼10vol-% monomers were able to increase their catalytic activities, consuming 65g/1 of glucose, producing 56g/1 of lactic acid, thus yielding 88% of product in general. But in free culture, the microorganism consumed almost all carbon sources and produced lactic acid only 60% even after 96 hours. The yield of the experiment under discussion was significantly high compared with conventional immobilization procedure.

• KSBB Journal
• /
• v.7 no.1
• /
• pp.79-83
• /
• 1992

The characteristics of Erwinia rhapontici cells with $\alpha$-glucosyltransferase activity immobilized in Ca-alginate beads and the performance of two different types of reactor-stirred tank reactor(STR) and packed bed reactor(PBR)-charged with these immobilized cells to produce palatinose from sucrose were investigated. The optimal pH(5.5-6.0) and temperature($30-35^{\circ}C$) showed no appreciable difference between free and immobilized cells. The apparent Km value of the immobilized cells(0.28M) was approximately two times higher than that of free cells(0.13M) at $30^{\circ}C$. The half life of the immobilized cells was found to be 380 h with STR while much greater operational stability was achieved with PBR. Continuous operation of PBR at a space velocity of $0.2h^{-1}$ for 30 days showed only 5% loss of initial activity.

• Progress in Medical Physics
• /
• v.13 no.3
• /
• pp.176-180
• /
• 2002

The demand for a better immobilization device has been increased in the radiation oncology field. Especially, it is essential to have a reliable and practical immobilization tool for the whole body radio-surgery and the IMRT(intensity modulated radiation therapy). A new method to immobilize the abdomen for the external beam radiation treatment was developed. The air-injected balloon blanket (AIBB) was designed as an immobilization device. As the air was injected into the AIBB, it pressed down the patient's abdomen and fixed the patient. The AIBB played a useful role to grab the patients' motion. Displacement of the abdomen in the anterior-posterior direction, which showed moving most during the respiration, reduced by more than 5 mm. Patients' movements from the breathing were reduced. The experimental results revealed that the AIBB could be used for the clinic.

• Korean Journal of Logic
• /
• v.14 no.1
• /
• pp.23-54
• /
• 2011

In this paper, I introduce what Boundary-Shifting theories of vagueness (or Contextualism about vagueness) are and what the Context-Fixing Argument is, which is the most powerful and plausible objection to Boundary-Shifting theories. The basic idea of the Context-Fixing Argument is that vagueness still remains even if we hold the context fixed. Many objections based on this simple idea can be found in the literature on Boundary-Shifting theories. It seems that, without a convincing response to the Context-Fixing Argument, Boundary-Shifters must be in trouble. But, oddly, defenders of Boundary Shifters have said very little about this matter. In this situation, ${\AA}$kerman and Greenough try to defend Boundary-Shifting theories of vagueness by suggesting several answers. In this paper, I critically examine their suggestions and develop a new answer to the Context-Fixing Argument.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.11
• /
• pp.1099-1104
• /
• 2012

The study investigates the mechanical deformation of a newly developed screwless omega-wire dynamic system for stabilization of the spine. The omega-wire spring stabilization system was tested under tension, compression, and dynamic compressive fatigue loads. In addition, its bending deformation was compared to that of a spiral-wire spring system using FEA. A model whose hanger inter-center distance is 60 mm showed an ultimate tensile stress of 3981.7 N at a displacement of 3.61 mm and an ultimate compressive load of 535.6 N at a displacement of 2.16 mm. Under fatigue loading of 5 Hz with 10 N/1 N, it did not show any failure over 5 million cycles, and the displacement was restricted to 8-9 mm. In the FEA, the omega-wire spring system showed more flexible bending features than did the spiral-wire spring system.