• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.111-112
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• 2002

The influence of aerated oil on a high-speed proceeding bearing is examined by using the classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing including the live surface tension of aerated oil. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The considered parameters for the study of bubbly lubrication are oil aeration level, air bubble size and shaft speed. The results show that, if the live surface tension is considered, the effect of air bubbles on the bearing load capacity is reduced due to temperature engagement comparing with that under the condition of a constant surface tension.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.11
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• pp.1477-1485
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• 2018

There are two major issues for activated sludge process in sewage treatment plant. One is how to make sewage be more clean and the other is the energy saving in sewage treatment process. The major monitoring sewage qualities are chemical oxygen demand, phosphorus, nitrogen, suspended solid in effluent. These are transmitted to the national TMS(Telemetry Monitoring System) at every hour. If these exceed the environmental standard, the environmental charges imposed. So, these water qualities are to be controlled below the environmental standard in operation of sewage treatment plant. And recently, the energy saving is also important in process operation. Over 50% energy is consumed in blowers and motors for injection oxygen into aeration tank. So, with the water qualities to be controlled below the environmental standard, the energy saving also is to be accomplished for efficient plant management. Almost researches are aimed to control water quality without considering energy saving. AI techniques have been used for control water quality. AI modeling simulator provided the optimal control inputs(blower speed, waste sludge, return sludge) for control water quality. Blower speed is the main control input for activated sludge process. To make sewage be more clean, the excessive blower speed is supplied, but water quality is not better than the previous. In results, non necessary energy is consumed. In this paper we propose a new method that the energy saving also is to be accomplished with the water qualities to be controlled below the environmental standard for efficient plant management. Water qualities in only aeration tank are used the inputs of fuzzy models. Outputs of these models are chemical oxygen demand, phosphorus, nitrogen, suspended solid in effluent and have the environmental standards. In test, we found this method could save 10% energy than the previous methods.

• Journal of Microbiology and Biotechnology
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• v.9 no.5
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• pp.548-553
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• 1999

A production of $\beta-Carotene$was attempted in a fed-batch culture of Blakeslea trispora by controlling both foam and dissolved oxygen in the presence of surfactant, Span 20. Results obtained from the shake flask cultures indicated that a high concentration of dissolved oxygen was needed for both cell growth and $\beta-Carotene$ synthesis, and the optimal concentration of glucose was found to be in the range of 50-100 g/l. In order to maintain the dissolved oxygen concentration level at higher than 50% of air saturation, pure oxygen was automatically sparged into the medium with air. Foam was controlled by bypassing air from the submerged aeration to the headspace in response to the foam that was caused by Span 20. High agitation speed was found to be detrimental to the cell growth due to shear damage, even though it provided sufficient dissolved oxygen. On the other hand, a low aeration speed caused stagnant regions in the fermentor because of improper mixing. Thus, for the fed-batch operation, agitation speed was increased gradually from 300 to 700 rpm to prevent cell damage at the initial stage of fermentation and to give efficient mixing for a viscous culture broth as the culture proceeded. By controlling dissolved oxygen and foam, a high concentration of $\beta-Carotene$otene (1,190 mg/l) was obtained in 6 days of the fed-batch culture of B. trispora with 2.5% of the dry cell weight, which was approximately 5 times higher than that of the batch cultures.

• Journal of Life Science
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• v.20 no.10
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• pp.1433-1442
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• 2010

Parameters related to dissolved oxygen for the production of pullulan by Aureobasidium pullulans HP-2001 were optimized in 7 l and 100 l bioreactors. The optimal concentrations of glucose and yeast extract for the production of pullulan were 50.0 and 2.5 g/l, respectively, and its conversion rate from glucose was 37% at a flask scale. The optimal initial pH of the medium and temperature for cell growth were 7.5 and $30^{\circ}C$, whereas those for the production of pullulan were 6.0 and $25^{\circ}C$. The optimal agitation speed and aeration rate for cell growth were 600 rpm and 2.0 vvm in a 7 l bioreactor, whereas those for the production of pullulan were 500 rpm and 1.0 vvm. The production of pullulan with an optimized agitation speed of 500 rpm and aeration rate of 1.0 vvm was 18.13 g/l in a 7 l bioreactor. Maximal cell growth occurred without inner pressure, whereas the optimal inner pressure for the production of pullulan was 0.4 kgf/$cm^2$ in a 100 l bioreactor. The production of pullulan under optimized conditions in this study was 22.89 g/l in a 100 l bioreactor, which was 1.38 times higher than that without inner pressure.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.3
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• pp.205-212
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• 2000

Experimental investigations on the removal of protein, total suspended solids and turbidity from aquacultural water were carried out by using three types of foam separator: counter current air driven type foam separator (CCADFS), high speed aeration type foam separator (HSAFS) and venturi type foam separator (VFS). The decrease of flow rate by CCADFS, HSAFS and VFS were $0.4,\;66.1,\;77.2 {\%}$ respectively. Protein removal rates by three types foam separator were decreased with the increased hydraulic residence time (HRT). Bellw 0.32 minute and 0.21 minute of hydraulic residence times, protein removal rate of HSAFS and YES was higher than that of CCADFS, respectively. Protein removal rate of VFS was lower than that of HSAFS at any HRT. As increasing the HRT, protein removal efficiency of CCADFS was increased, but that of HSAFS and VES were decreased. The changes of removal rates and efficiencies of total suspended solid and turbidity were similar to proteins.

• The Korean Journal of Food And Nutrition
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• v.11 no.6
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• pp.606-611
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• 1998

For waste recyle, we were investigated on Gardenia blue color production using Gardenia by-product by Bacillus subtilits. Optimum conditions for producing blue pigment were found to be 30$^{\circ}C$, initial pH 6.5, glucose as a carbon source 3% and yeast extract as a nitrogen source 0.5%, respectively. Optimum conditions for fermentor culture were agitation speed 400rpm, aeration 2 vvm and inoculum 5%. The optimum perculture time for inoculum was 20 hrs for blue pigment production.

• Microbiology and Biotechnology Letters
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• v.22 no.4
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• pp.389-394
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• 1994

8 X 10$^{6}$(viable cells/ml) of maximum cell density and 9000(IU/ml) of $\gamma$-IFN production were obtained at 55(ml/hr) of a perfusion rate by cultivating HSF cells using a moving membrane aeration bioreactor. This system proves to be an efficient culture process by maintaning 90% of viable cells during the whole cultivation periods. The metabolic molar quotient of glucose to lactate was 0.81 for overall ranges of glucose consumed while the evolution of ammonia was not linearly related to the consumption of glutamine. Low molar conversion ratio was observed in low consumptions of glutamine and high molar conversion ratio in high comsumptions. It also shows that the glutamolysis plays important role in the steady state conditions by evolving larger quantities of ammonia than lactate. At the above of 50 rpm, which is the optimum agitation speed for this bioreactor, the cell growth was severely affected while the IFN production was less decrea- sed, maintaing 1.5 X 10$^{-3}$(IU/cell/day) specific IFN production rate. The cumulatvie $\gamma$-IFN production was 7.2 X 10$^{8}$(IU) for 70 days of the cultivation, which yields 1 X 10$^{7}$ (IU/day) of IFN production rate. Therefore, a commercial production of $\gamma$-IFN by this culture process can be achievable by maintaining the above IFN productivity in a scaled-up culture system.

• Microbiology and Biotechnology Letters
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• v.24 no.6
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• pp.756-762
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• 1996

In order to develop the method for mass production of natural food colorant from Monascus anka, optimum cultivation conditions for producing red and yellow pigments by cultiva- ting the mold in a jar fermenter and their color characteristics were investigated. The mold produced red and yellow pigments both intracellularly and extracellularly. These pigments showed unique light absorption characteristics with maximum absorption of 494, 380, 506, and 388 nm for extracellular red pigment (ERP), extracellular yellow pigment (EYP), intracellular red pigment (IRP), and intracellular yellow pigment (IYP), respectively. Optimum conditions for producing red pigments were found to be temperature 30$\circ$C, initial pH 6.0, rice powder 3-5%, peptone 0.05%, magnesium sulfate 0.25%, aeration rate 0.1 vvm. Optimum temperature for producing yellow pigments was around 35$\circ$C which is higher than that of producing red pigments. The initial pH and rice powder concentration for producing yellow pigments were the same as those of producing red pigments. The higher concentration of nitrogen source and inorganic salt, aeration rate, the more the yellow pigments were produced. The optimum agitation speed was 100 - 300 rpm for pigment production.

• KSBB Journal
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• v.13 no.6
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• pp.700-705
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• 1998

Studies were made to investigate effects of the scale-up of stirred tank bioreactors on cell growth and alkaloids production for suspension cultures of Eschscholtzia californica. In the 1.5 L STR, cell lysis was observed at 110 rpm or higher agitation speed. The agitation speed of 30 L STR was 43.7 rpm to maintain the same shear stress developed in 1.5 L STR of 100 rpm. As a result of scale-up from 1.5 L to 30 L STR, the specific growth rate was decreased from 0.12 to 0.07 day-1. The alkaloids productivity was also decreased from 0.24 to 0.14 mg/L-day. Changes of mixing performance and oxygen transfer were studied to explain the decrease of cell growth and alkaloids production. Decreased oxygen transfer rate coefficient(KLa) and increased mixing time by the scale-up was observed at various aeration rates.

• Horticultural Science & Technology
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• v.30 no.4
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• pp.432-436
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• 2012

This study was conducted to determine the optimal aeration rate for mass propagation of ever-bearing strawberry by bioreactor culture. The aeration rate was treated in four levels: 0.1 vvm (air volume/medium volume/min), 0.2 vvm, 0.3 vvm, and 0.4 vvm. In 0.2 vvm conditions, shoot length was the longest at 9.03 cm in bioreactor culture, leave numbers were 40.4 ea and fresh weight was 6,106 mg. Plant growth rate at 0.2 vvm condition was faster than other treatments. In the aeration condition, 0.2 vvm was most effective to increase aerial part growth and to decrease medium consumption. As the culture periods increased, the fresh weight also increased rapidly. After six weeks of cultivation, shoots were emerged with 10.4 ea per plantlet, resulting in developing a complete plant. As a result, the bioreactor culture system for mass propagation of strawberry is required to continuously supply the air by 0.2 vvm speed and cultivate at least for six weeks.