• KSBB Journal
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• v.18 no.2
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• pp.155-160
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• 2003

The effect of dissolved oxygen(DO) on microbial transglutaminase(mTG) production by Streptoverticillium morbaraense was studied in on-line computer controlled fermentation system. In order to control dissolved oxygen during fermentation, the agitation speed and aeration rate of 2.5 L fermenter ranged from 260 to 360 rpm and 0.3 to 3.9 L/min, respectively. The maximum microbial transglutaminase production was obtained at controlled 20% of dissolved oxygen among the various dissolved oxygen controlled batch cultures tested. The production of microbial transglutaminase at controlled 20% of dissolved oxygen was about 2.12 U/mL which was 1.1 times higher than that obtained in batch culture without control of dissolved oxygen. Also, the highest microbial transglutaminase production was obtained in fed-batch cultures in which dissolved oxygen was controlled at 20%, and it was improved almost 1.3 times in comparison with that without control of dissolved oxygen. Maximal dry cell weight and microbial transglutaminase production were 13.2 g/L and 2.6 U/mL, respectively. Finally, it was also found that fed-batch fermentation at controlled 20% of dissolved oxygen showed a good performance for the microbial transglutaminase production by on-line computer controlled fermentation system which may be generally applicable to other microbial cultures.

• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.5
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• pp.352-358
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• 2001

Because algal cells are so efficient at absorbing incoming light energy, providing more light energy to photobioreactors would simply decrease energy conversion efficiency. Furthermore, the algal biomass productivity in photobioreactor is always proportional to the total photosynthetic rate. In order to optimize the productivity of algal photobioreactors (PBRs), the oxygen production rate should be estimated. Based on a simple model of light penetration depth and algal photosynthesis, the oxygen production rate in high-density microalgal cultures could be calculated. The estimated values and profiles of oxygen production rate by this model were found to be in accordance with the experimental data. Optimal parameters for PBR operations were also calculated using the model.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.171-174
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• 2000

The effect of the dissolved oxygen (DO) concentration on the production of manganese peroxidase by Phaenerochaete chrysosporium was studied in the immobilized reactor system. The oxygen levels significantly affected the production of manganese peroxidase (MnP) as well as that of $H_2O_2$. It is known that a high oxygen level is required to produce this enzyme. In this study, however, higher DO concentrations above a critical DO concentration inhibited MnP production. It is thought that a greater $H_2O_2$ production seen with higher DO concentrations caused adverse effects on the MnP production. On the other hand, with lower DO concentrations, $H_2O_2$ did not accumulate enough to stimulate MnP production.

• Journal of Microbiology and Biotechnology
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• v.20 no.2
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• pp.346-349
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• 2010

Coenzyme $Q_{10}$ ($CoQ_{10}$) production from Rhizobium radiobacter T6102 was monitored under various oxygen supply conditions by controlling the agitation speeds, aeration rates, and dissolved oxygen levels. As the results, the $CoQ_{10}$ production was enhanced by limited oxygen supply. To investigate whether the $CoQ_{10}$ production is associated with its physiological functions of electron carrier and antioxidant, the effects of sodium azide and hydrogen peroxide on the $CoQ_{10}$ production were studied, showing that the $CoQ_{10}$ contents were slightly enhanced with increasing sodium azide (up to 0.4 mM) and hydrogen peroxide (up to $10\;{\mu}M$) concentrations. These results suggest the plausible mechanism where the limited electron transfer stimulating the environments of limited oxygen supply and oxidative stress could accumulate the $CoQ_{10}$, providing the relationship between the $CoQ_{10}$ physiological functions and its regulation system.

• Journal of Microbiology
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• v.37 no.3
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• pp.159-167
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• 1999

The effects of bicarbonate concentration, atmospheric carbon dioxide level, and reduced atmospheric oxygen on biomass and geosmin production and geosmin/biomass (G/B) values for Streptomyces halstedii, a producer of the off-flavor compound geosmin, were determined. In addition, a study was performed to determined possible synergistic relationships between a cyanobacterium, Oscillatoria tenuis UTEX #1566, and S. halstedii in the enhancement of actinomycete growth and/or geosmin production. These studies took into consideration those conditions that can occur during cyanobacterial bloom die-offs. Increasing bicarbonate concentration caused slight decreases in geosmin production and G/B for S. halstedii. Increasing atmospheric oxygen promoted geosmin production and G/B while lower oxygen levels resulted in a decrease in geosmin production and G/B by S. halstedii. Biomass production by S. halstedii was adversely affected by reduced oxygen levels while changes in bicarbonate concentration and atmospheric carbon dioxdie levels had little effect on biomass production. Sonicated cells of O. tenuis UTEX #1566 promoted biomass production by S. halstedii, and O. tenuis culture (cells and extracellular metabolites) and culture supernatnat (extracellular metabolites) each promoted geosmin and G/B yields for S. halstedii. In certain aquatic systems, environmental conditions resulting from cyanobacterial blooms and subsequent bloom die-offs could favor actinomycete growth and off-flavor compound by certain actinomycetes.

• The Journal of Korean Medicine
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• v.18 no.2
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• pp.355-365
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• 1997

This study was undertaken to examine the effect of Cheongahwan(CAH), being known to reinforce Kidney-yang, on the activities of endogenous antioxidant enzymes and the production of oxygen free radicals in the kidney tissues. Alterations in enzyme activities were observed after in vivo treatment in rats. CAH caused a significant increase in the activities of superoxide dismutase (SOD), glutathione peroxidase and glutathione S-transferase. But catalase activity was not significantly altered by CAH. Treatment in vitro of CAH decreased the production of oxygen free radicals in a dose-dependent fashion. These results suggest that CAH stimulate the activities of antioxidant enzymes and inhibit directly the production of oxygen free radicals. These effects of CAH may contribute to prevent the oxygen free radical-induced impairment of cell function.

• Journal of Microbiology and Biotechnology
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• v.5 no.2
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• pp.100-104
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• 1995

Production of $poly-{\beta}-hydroxybutyrate$ (PHB) in a strain of Azotobacter chroococcum, a nitrogen-fixing bacteria, was investigated at various levels of nitrogen and oxygen. Feeding nitrogen source increased both cell growth and PHB accumulation. Oxygen supply appeared to be one of the most important operating parameters for PHB production. Both cell growth and PHB accumulation increased with the sufficient supply of air in the fed-batch fermentation of the strain. However, it was also noted that keeping the oxygen level under limited condition was critical to achieve high PHB productivity. A high titer of PHB (52 g/l) with a high cellular content (60%) was obtained after 48 hr of fed-batch operation by controlling the oxygen supply. Dual limitation of nitrogen and oxygen did not further increase the PHB accumulation probably due to the greater demand for reducing power and ATP for nitrogen fixation.

• Microbiology and Biotechnology Letters
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• v.26 no.6
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• pp.529-536
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• 1998

In a 20 L fermentor experiments the level of dissolved oxygen (D.O.) strongly affected growth and PHBV production of Azotobacter vinelandii UWD. A higher D.O. (5%) increased specific cell growth rate two folds but PHBV production was 17 folds higher (62.3 wt%) at a lower D.O.(1%) level. D.O. level was not a good criterion to evaluate the effect of aeration on fermentation characteristics of A. vinelandii UWD. This strain maintained an equal D.O. (5%) by decreasing its oxygen consumption rate when oxygen transfer rate (OTR) was decreased by changing agitation speed at a fixed aeration rate. OTR rather than D.O. was a criterion to explain the effect of aeration on the cell growth and PHBV production. At 5% D.O. with a lower 0TR cell growth rate decreased but PHBV production (57.3 wt%) approached to that (62.3 wt%) of the lower (1%) D.O.

• Journal of Microbiology and Biotechnology
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• v.25 no.1
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• pp.81-88
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• 2015

This study describes a novel strategy to regulate the metabolic flux for lactic acid production in Lactobacillus casei. The ldhL gene encoding _L-lactate dehydrogenase (L-LDH) was overexpressed in L. casei, and a two-stage oxygen supply strategy (TOS) that maintained a medium oxygen supply level during the early fermentation phase, and a low oxygen supply level in the later phase was carried out. As a consequence, a maximum L-LDH activity of 95.6 U/ml was obtained in the recombinant strain, which was over 4-fold higher than that of the initial strain. Under the TOS for L. casei (pMG-ldhL), the maximum lactic acid concentration of 159.6 g/l was obtained in 36 h, corresponding to a 62.8% increase. The results presented here provide a novel way to regulate the metabolic flux of L. casei for lactic acid production in different fermentation stages, which is available to enhance organic acid production in other strains.

• Current Photovoltaic Research
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• v.4 no.3
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• pp.124-129
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• 2016

Recently industry has voiced a need for optimally designing the production process of low-cost, high-quality ingots by improving productivity and reducing production costs with the Czochralski process. Crystalline defect control is important for the production of high-quality ingots. Also oxygen is one of the most important impurities that influence crystalline defects in single crystals. Oxygen is dissolved into the silicon melt from the silica crucible and incorporated into the crystalline a far larger amount than other additives or impurities. Then it is eluted during the cooling process, there by causing various defect. Excessive quantities of oxygen degrade the quality of silicone. However an appropriate amount of oxygen can be beneficial. because it eliminates metallic impurities within the silicone. Therefore, when growing crystals, an attempt should be made not to eliminate oxygen, but to uniformly maintain its concentration. Thus, the control of oxygen concentration is essential for crystalline growth. At present, the control of oxygen concentration is actively being studied based on the interdependence of various factors such as crystal rotation, crucible rotation, argon flow, pressure, magnet position and magnetic strength. However for methods using a magnetic field, the initial investment and operating costs of the equipment affect the wafer pricing. Hence in this study simulations were performed with the purpose of producing low-cost, high-quality ingots through the development of a process to optimize oxygen concentration without the use of magnets and through the following. a process appropriate to the defect-free range was determined by regulating the pulling rate of the crystals.