• KSBB Journal
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• v.11 no.3
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• pp.353-359
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• 1996

The experiments were conducted in the leaching of aqueous uranium from low-grade uranium ore by Thiobacillus ferrooxidans. The optimal concentration of ferrous iron in 9K medium was 16.2g/L when the uranium ore concentration in slurry was 40g/L. The leaching rates were increased by decreasing the particle size of uranium ore and by increasing uranium ore concentration. In the leaching experiments in an agitated vessel reactor, only 39.3% of uranium was leached out within 12 days, which was comparable as that in the shaking incubator, without any notable improvement. Hence, it was observed that an agitated vessel reactor was not effective in the leaching of uranium from uranium ore by T. ferrooxidans. In the leaching experiments in a draught-tube reactor, the maximum concentration of uranium leached and cell number were a 12.8mg/L and $2.47{\times}1010cells/mL$ respectively. The uranium yield reached up to 91.4% within 11 days culture due to enhanced aeration and mixing characteristics of draught-tube reactor as compared to agitated vessel reactor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.986-989
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• 2008

Recently the agitator are being widely used in the machine plan in order to increase the petrochemical industry. The agitator normally consist of impeller, shaft, hub, reduction gear and the driving motor. It is one of the key design issue to confirm that the vibration caused by the rotation of the shaft should not coincide with the natural frequency of the shaft itself. And petrochemical industry as well as plants have been in operation for long period beyond their original design lives. In this paper the vibration of Ox-Reactor Agitator is measured for check machine condition. The result of diagnosis and solution is discussed in this paper.

• KSBB Journal
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• v.9 no.2
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• pp.211-223
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• 1994

In fermentations with a 4-liter stirred tank bioreactor, a better than two-fold enhancement of the gas-liquid mass transfer coefficient$(k_La)$ in the celite-immobilized fungal cultures of Tolypocladium in flatum over the parallel conventional free-cell was observed at identical biomass concentrations, despite the higher specific oxygen uptake rate of the immobilized fungi during exponential growth. As a result oxygen sufficient conditions, i. e., dissolve oxygen(D.O.) concentrations exceeding 75% air saturation, could be maintained throughout exponential growth period of the immobilized culture, in contrast to the suspended fungal culture, whose D.O. levels fell below 50% air saturation. A linear monotonic dependence of $k_La$ upon impeller agitaion rate was found for both immobilized and conventional cultivation modes over a range of 250 to 550rpm, the slope being a function of biomass concentration for the free but not for the immobilized cell system In contrasts oxygen transfer rate was a much weaker function of aeration rate up to about 2.5 vvm for both culture configurations. Above this level, aeration rate had no further effect on the mass transfer. In addition, the immobilized cultures sustained good morphological and physiological states, leading to almost two times higher cyclosporln A (CyA) productivity overt the parallel free cell system. These experiments suggest that the celite-immobilized fungal system in a stirred tank reactor has considerable promise for scaling up cyclosporin A production in terms of high-density cultivation.

• KSBB Journal
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• v.14 no.4
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• pp.440-444
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• 1999

For the effecient production of clavulanic acid., a mutant strain Streptomyces clavuligerus KK was selected from Streptomyces clavuligerus ATCC 27064 through mutation with NTG. S. clavuligerus ATCC 27064 produced about 200 mg/L of calvulanic acid when the medium was composed of 1%(W/V) glycerol, 1.5%(W/V) soybean flour, 0.1%(W/V) $KH_2PO_4$, 0.2%(V/V) soybean oil. A selected mutant, S. clavuligerus KK, produced about 1150 mg/L of clavulanic acid in the same medium. After the addition of $MgSO_4$ to the basal medium, S. clavuligerus KK produced about 1550 mg/L of clavulanic acid, with shows about 1.3 times higher than that produced in the basal medium. In order to select the proper bioreactor for the production of clavulanic acid, a batch culture was performed in an airlift, a bubble column and an stirred tank bioreactors. In an airlift bioreactor, about 1350 mg/L of clavulanic acid was produced, in a bubble column bioreactor, about 1550 mg/L, in a stirred tank bioreactor, about 2200 mg/L, respectively. The production of clavulanic acid in stirred tank bioreactor was about 50% higer than that by an airlift and a bubble column bioreactors. According to this result, the stirred tank bioreactor was selected as a proper bioreactor.

• Korean Journal of Food Science and Technology
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• v.35 no.3
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• pp.417-422
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• 2003

The onions are considered to be a favorable functional source of beverage because they contain much sugar and various nutrients, and they are juicy vegetable. Recently, consumers have a new trend to take functional foods with health benefits. To meet this need, this study was the basic research to establish a manufacturing process of functional onion beverage by glucose oxidase. Glucose oxidase catalyzes reaction of glucose oxidation and makes generation of gluconic acid. Kinetics of the reaction was also investigated, and maximum glucose consumption rate $(V_{max})$ of $26.1{\times}10^{-2}\;g/L{\cdot}min$ and $K_m$ of 5.84 g/L were obtained. Optimum conditions were obtained when the glucose oxidase catalyzed reaction was carried out at temperature of $25^{\circ}C$, agitation rate of 450 rpm and aeration rate of 4 vvm in a 2.5 L jar fermentor. Finally, the enzyme reactor was 10-times scaled up and a similar glucose oxidation performance was achieved in the scaled-up reactor.

• Korean Journal of Organic Agriculture
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• v.20 no.4
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• pp.703-713
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• 2012

Three types of aeration system were installed in experimental liquid fertilization tanks to investigate the change of characteristics of pig slurry used as a raw material for making livestock liquid fertilizer. The aeration systems of the reaction tanks were composed of three major part: the air suppling part (blower), the air pipe part, and the air diffuser part. In the first tank (reactor A), the air was supplied from the bottom of the reaction tank through air pipe system connecting air diffuser with commercial ordinary blower. In the second tank (reactor B), the air diffuser was located 10cm above the bottom of the reactor. In the third tank (reactor C), the pure air was supplied with circulating pjg slurry. The oxygen content of pure air was about 90%. The pure air was mixed with pig slurry by mechanically in the air suppling part (blower) and the air pipe part. The agitation effect was highest in the reactor C than other reactors. The contents of SS, COD, T-N and T-P of each samples collected at middle part of all reactors were 8,500, 4,188, 694 and 422mg/L; 9,000, 4,247, 813 and 356mg/L; 8,667, 6,910, 973 and 269mg/L, respectively.

• Applied Chemistry for Engineering
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• v.30 no.4
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• pp.493-498
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• 2019

In polymer exchange membrane fuel cells, it is crucial to fabricate a highly active and thin Pt catalyst layer for the smooth mass transport of dissolved oxygen and water. Although a highly loaded platinum (Pt) catalyst based on the hydrothermal synthesis has been reported in several studies, its growing behaviors and kinetics were yet to be understood. In this study, we investigated the growth of Pt crystal in suspension after the reduction step depending on a stirring time and evaluated the electrochemical activity. For only a couple of hours in the early stage, Pt colloids were adsorbed on the Pt-carbon catalyst and the Pt crystal was grown. After that, the small Pt colloid was formed by another nucleation step, which did not involve the growth of Pt crystal. We reveal that the Pt-Carbon catalyst with stirring for 6 h showed a high activity toward the oxygen reduction reaction.

• Microbiology and Biotechnology Letters
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• v.29 no.4
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• pp.240-247
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• 2001

The effect of microsparged aeration in mammalian cell bioreactor on the oxygen transfer rate and cell viability was studied. The microspargers with differ- ent micron-sized pores were used to supply oxygen to the medium. The oxygen transfer coefficients (k$_{L}$a) measured in the bioreactor were markedly increased, which is due to the increase of the contacting area between air bubbles and liquid medium when the pore size of microsparger decreases. When the impellers of two different types (square-pitch marine impeller and $45^{\circ}$ pitched flat blade impeller) were used for agitation, the k$_{L}$a values were slightly higher with the marine impeller than with the blade impeller. The detrimental effect of direct gas sparging with microsparger on mammalian cells was investigated in bubble columns with various air flow rates and different pore sized microspargers. The first-order cell death rate constant ($k_{d}$ /7) was shown to be directly proportional to the air flow rate and inversely proportional to the pore size. During the cultivation of hybridoma cells using microsparger with the pore size of $0.57\mu$m in the mammalian cell culture bioreactor, the continuous sparging caused the cell death and suppressed the cell growth. However, cells grew normally and cell viability was maintained above 90% in the logarithmic phase when the air was intermittently sparked in order to maintain the dissolved oxygen level above 20%.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.239-242
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• 2000

Experimental studies on the effects of impeller to provide the microbial transglutaminase derived from Streptoverticillium mobaraense have been conducted. The optimal production medium was determined by latin-square design, and the effects of aeration and agitation were observed by using different sizes and shapes of impellers for the poduction of transglutaminase. The effects of pH and temperature were also evaluated for the production of transglutaminase in flasks. As a result, pH is more effective than temperature for both enzyme production and growth of the microorganism. The peak enzyme activity for transglutaminase in fermenter was 0.7 U/mL, but this was still well below the avereage enzyme activity, 1,3 U/mL, obtained in flask runs.

• Microbiology and Biotechnology Letters
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• v.48 no.3
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• pp.344-357
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• 2020

Strain improvement and bioprocess development were undertaken to enhance hyaluronic acid(HA) production by Streptococcus zooepidemicus cells. Using a high-yielding mutant strain, statistical medium optimization was carried out in shake flask cultures, resulting in 52% increase in HA production (5.38 g/l) at the optimal medium composition relative to the parallel control cultures. For sufficient supply of dissolved oxygen (DO), which turned out to be crucial for enhanced production of HA, agitation system and speed were intensively investigated in 5 L bioreactor cultures. Increase in oxygen mass transfer coefficient (k_La) through increment of agitation speed (rpm) and 35% expansion of diameter of the newly-designed impellers showed significantly positive effects on HA production. By installing an expanded Rushton-turbine impeller for efficient break-down of sparged air, and an extended marine impeller above the Rushton-turbine impeller for efficient mixing of the air-born viscous fermentation broth, maximum amount of HA (9.79 g/l) was obtained at 450 rpm, 1.8 times higher level than that of the corresponding flask culture. Subsequently, the possibility of bioprocess scale-up to a 50 L bioreactor was investigated. Despite almost identical maximum HA production (9.11 vs 9.25 g/l), the average HA volumetric productivity (r_p) of the 50 L culture turned out only 74% compared to the corresponding 5 L culture during the exponential phase, possibly caused by shear damages imposed on the producing cells at the high stirring in the 50 L culture. The scale-up process could be successfully achieved if a scale-up criterion of constant oxygen mass transfer coefficient (k_La) is applied to the 50 L pilot-scale bioreactor system.