• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.541-544
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• 2001

One of the most promising TCE treatment systems is trickling biofilter (TBF), in which monooxygenase, the corresponding enzyme for initiating growth substrate oxidation, fortuitously transforms TCE via cometabolism. TCE. however. is not easily treated by simple cometabolic biotransformation. This is mainly due to the toxicity of TCE to microbial cell and monooxygenase. In this study, we cleveloped and operated a two-stage CSTR/TBF system for the long-term continuous treatment of TCE. In the two-stage biotransfon11ation system, CSTR with cell recycle from TBR was coupled to the TBR for the reactivation of the cells deactivated during TCE degradation.

• Microbiology and Biotechnology Letters
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• v.13 no.3
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• pp.245-250
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• 1985

In order to increase citric acid productivity. several attempts were made; isolation and characterization of the mutant strain produced citric acid in a high yield, citric acid fermentation in a medium containing relatively higher amount of glucose and citric acid production by the use of semicontinuous ceil recycle system. By the treatment of Candide lipolytica S-109 with NTG, a mutant J-24 was selected as the highest producer of citric acid among the strains formed larger CaCO$_3$ lytic zone. it produced 72g/1 citric acid in 10％ glucose medium. Because mutant J-24 produced 85g/l citric acid and showed 53％ yield in 16％ glucose medium, several factors were adjusted to increase the yield in 16％ glucose medium. 0.8-1.0$\times$10$^{-3}$ P/C ratio, 0.15％ urea, 0.25％ yeast extract were suitable at citric acid production in 16％ glucose medium. Under this condition, J-24 strain produced 93g/l citric acid and showed 58％ yield. Semicontinuous cell recycle system was used to protons the effective production phase, to minimize the product inhibition and to shorten the lag phase. The productivity of semicontinuous cell recycle system was 0.79g/l h while that of batch system was 0.53g/l.h

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.5
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• pp.678-685
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• 2011

An Ejector enhances system efficiency, are easily operated, have a mechanically simple structure, and do not require a power supply. Because of these advantages, the ejector has been applied to a variety of industrial fields such as refrigerators, power plants and oil plants. In this work, an ejector was used to safely recycle anode tail gas in a 75-kW Molten Carbonate Fuel Cell (MCFC) system at KEPCO Research Institute. In this system, the ejector is placed at mixing point between the anode tail gas and the cathode tail gas or the fresh air. Commercial ejectors are not designed for the actual operating conditions for our fuel cell system. A new ejector was therefore designed for use beyond conventional operating limits. In the first place, a few sample ejectors were manufacured and the entrainment ratio was measured at a dummy stack. Through this experiment, the optimum ejector was chosen. The 75-kW MCFC system equipped with this optimum ejector was operated successfully.

• Journal of Energy Engineering
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• v.8 no.4
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• pp.592-604
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• 1999

The steady state and dynamic characteristics of large cell area MCFC stacks were analyzed to solve the problems such as temperature difference generated in stacks and pressure difference between anode and cathode. Manipulated variables (current density, duel utilization rate, oxidant utilization rate) and controlled variables (temperature difference, anode and cathode pressure difference) which had an important effect on the MCFC stack performance were determined using operation results of two types of MCFC stacks (5kW (3,000 $\textrm{cm}^2$, 20 ea). 3kW (6,000 $\textrm{cm}^2$, 5ea)). The stability and transfer function representing system dynamics were obtained by steady state gain rate which showed the relative change between MVs and CVs. The transfer function was a 3$\times$3 matrix and a typical first order system without time delay. The optimal operating condition of large cell area MCFC stacks could be determined by analyzing dynamic characteristics. In case of a 5 kW MCFC stack, pressurized operation with recycle flow should be used to control the outlet temperature less than 68$0^{\circ}C$ and to control the MCFC system effectively. MIMO control or decoupler should be used to remove the interaction between MVs and CVs. This result will be used as important data in determining the control structure design and operation mode of large cell area MCFC systems in the future.

• Journal of Microbiology and Biotechnology
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• v.16 no.12
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• pp.1874-1881
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• 2006

Flocculation of Candida tropicalis HY200 was systemically investigated to elucidate its mechanism, and used for cell cycles in repeated-batch cultivations for the production of xylitol from xylose. Flocculation occurred only after the late exponential phase of growth in the culture media and buffer within the narrow pH range of 3.0-5.0. The flocculation was completely inhibited by treatments of cells with proteases and partially reduced by treatments with carbohydrate-hydrolyzing enzymes and by the presence of mannose and glucose. The addition of calcium ions significantly enhanced the flocculation during cultivation, which was completely abolished by the addition of EDTA. The flocculent yeast HY200 provided repeated-batch cultivations employing cell recycles by flocculation over 6 rounds of cultivation for the production of xylitol from xylose, resulting in a relatively high productivity of averaged 4.6 g xylitol/l h over six batches and maximal 6.3 g xylitol/l h in the final sixth batch. Cell recycle by flocculation was fast and convenient, which could be applicable for the industrial scale of xylitol production.

• Journal of the Korean Society of Industry Convergence
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• v.10 no.2
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• pp.73-80
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• 2007

The preparation of oil absorbent using waste polyurethane was studied. And the effects of shape, size, and contents of waste polyurethane foam was investigated. The waste foam was treated in shape of powder, cube and bar type generated from rigid sandwich panel process. The tests for flexural strength, combustibility, and water absorptivity were carried out to investigate the mechanical and physical properties of the recycled foams. And the cell microstructure was evaluated through Scanning Electron Micrograph. The recycled foam containing powder-shaped underfilled and showed poor properties that was generated through reactivity of the resins and increasing of slurry viscosity. For the recycled foam with the cube and bar-shaped, the underfilling was caused by interference between the waste PUFs and increasing surface areas of PUF. Low cell density, non-uniformity of cell shape and size, and low adhesion of the boundary surface (new/recycled) was showed as a result of the poor properties. Considering underfilling and the properties of PUF (new/recycled), maximum recycle contents were less than 20 wt% for the powder and above 40 wt% for the cube and bar.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.3
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• pp.284-288
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• 2005

Baker's yeast was disrupted in a 1.4-L stainless steel horizontal bead mill under a continuous recycle mode using 0.3 mm diameter zirconia beads as abrasive. A single pass in continuous mode bead mill operation liberates half of the maximally released protein. The maximum total protein release can only be achieved after passaging the cells 5 times through the disruption chamber. The degree of cell disruption was increased with the increase in feeding rate, but the total protein release was highest at the middle range of feeding rate (45 L/h). The total protein release was increased with an increase in biomass concentration from 10 to $50\%$(w/v). However, higher heat dissipation as a result of high viscosity of concentrated biomass led to the denaturation of labile protein such as glucose 6-phosphate dehydrogenase (G6PDH). As a result the highest specific activity of G6PDH was achieved at biomass concentration of $20\%$(ww/v). Generally, the degree of cell disruption and total protein released were increased with an increase in impeller tip speed, but the specific activity of G6PDH was decreased substantially at higher impeller tip speed (14 m/s). Both the degree of cell disruption and total protein release increased, as the bead loading increased from 75 to $85\% (v/v)$. Hence, in order to obtain a higher yield of labile protein such as G6PDH, the yeast cell should not be disrupted at biomass concentration and impeller tip speed higher than $20\%(w/v)$ and 10 m/s, respectively.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.121-124
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• 2000

Organic acids were produced from wastes streams in food industries by cell-recycle fermentation using Propionibacterium acidipropionici ATCC 4965. As a results of continuous fermentation, maximum productivity was 3.32g organic acid/L/hr at the dilution rate of 0.2/hr. Compared to batch fermentation, maximum productivity was improved by as much as 13 times and cell mass production was increased by as much as 22 times. The diluted organic acids in the fermenter were selectively separated by liquid-liquid extraction using 30%(w/w) trioctylamine(TOA) dissolved in methylisobutylketone(MIBK). The degree of extraction was reached above 90% for both acetic and propionic acid through repeated extraction of organic acids in fermentation broth.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.1
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• pp.1-9
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• 2012

This paper explained about the sludge recycling system which retrieved the silicon and abrasive from solar cell wafer slicing. The basic process of the recycling system was multiple centrifuge and secondary processes of ultra sonic agitation, addition of alcohol-water solution and heating sludge was added for raising separation efficiency. The recycling rate was about 96% and 94% for 2N, 4N silicon respectively. The SiC abrasive recycling rate was about 80%. To retrieve the high purity of 4N silicon, the heat process in vacuum furnace was added to remove remaining impurity components.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.5
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• pp.269-278
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• 2003

Gibberellic acid (GA$_3$) is a commercially important plant growth hormone, which is gaining much more attention all over the world due to its effective use in agriculture and brewing industry. Industrially it is produced by submerged fermentation technique using Ascomycetous fungus Gibberella fujikuroi. Solid state and immobilized cell fermentation techniques had also been developed as an alternative to obtain higher yield of GA$_3$. This review summarizes the problems of GA$_3$ fermentation such as production of co-secondary metabolites along with GA$_3$, substrate inhibition and degradation of GA$_3$ to biologically inert compound gibberellenic acid, which limits the yield of GA$_3$ in the fermentation medium. These problems can be overcome by various bioprocessing strategies e.g. two - stage and fed batch cultivation processes. Further research on bioreactor operation strategies such as continuous and / or extractive fermentation with or without cell recycle / retention system need to be investigated for improvement in yield and productivity. Down stream processing for GA$_3$ isolation is also a challenge and procedures available for the same have been critically evaluated.