• Microbiology and Biotechnology Letters
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• v.20 no.5
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• pp.588-596
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• 1992

The fermentation characteristics of ethanol production by the use of immobilized Zymomonas mobilis KCTC 1534 cells were investigated in terms of formation factors such as substrate and product concentration. In batch fermentation, the maximum values of specific ethanol productivity, specific substrate uptake rate, ethanol yield, and glucose conversion rate were $29.14g/{\ell}{\cdot}h$, $60.24g/{\ell}{\cdot}h$, 0.48g/g, and 98.4%, respectively, with 17% glucose medium, and its ethanol productivity was $2.91g/{\ell}{\cdot}h$ in the case of 25 hour fermentation time. Repeated batch fermentation was possible for 30 days with 2.24-$2.94g/{\ell}{\cdot}h$ ethanol productivity. In semicontinuous fermentation, the maximum ethanol productivity was shown to be $15.7g/{\ell}{\cdot}h$ at $0.36h^{-1}$ effective dilution rate with 17% glucose concentration. In this case, ethanol yield coefficient and glucose conversion rate were 0.39 g/g, 64.7%, respectively.

• Korean Journal of Materials Research
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• v.23 no.7
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• pp.359-365
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• 2013

We investigated the nanostructural, chemical and optical properties of nc-Si:H films according to deposition conditions. Plasma enhanced chemical vapor deposition(PECVD) techniques were used to produce nc-Si:H thin films. The hydrogen dilution ratio in the precursors, [$SiH_4/H_2$], was fixed at 0.03; the substrate temperature was varied from room temperature to $600^{\circ}C$. By raising the substrates temperature up to $400^{\circ}C$, the nanocrystalite size was increased from ~2 to ~7 nm and the Si crystal volume fraction was varied from ~9 to ~45% to reach their maximum values. In high-resolution transmission electron microscopy(HRTEM) images, Si nanocrystallites were observed and the crystallite size appeared to correspond to the crystal size values obtained by X-ray diffraction(XRD) and Raman Spectroscopy. The intensity of high-resolution electron energy loss spectroscopy(EELS) peaks at ~99.9 eV(Si $L_{2,3}$ edge) was sensitively varied depending on the formation of Si nanocrystallites in the films. With increasing substrate temperatures, from room temperature to $600^{\circ}C$, the optical band gap of the nc-Si:H films was decreased from 2.4 to 1.9 eV, and the relative fraction of Si-H bonds in the films was increased from 19.9 to 32.9%. The variation in the nanostructural as well as chemical features of the films with substrate temperature appears to be well related to the results of the differential scanning calorimeter measurements, in which heat-absorption started at a substrate temperature of $180^{\circ}C$ and the maximum peak was observed at ${\sim}370^{\circ}C$.

• Journal of Korean Society on Water Environment
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• v.39 no.6
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• pp.439-450
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• 2023

The Yeongsan River, a major water resource for Jeollanam-do, that is adjacent to industrial complexes and agricultural areas, is exposed to water pollution. Therefore, it is necessary to investigate the impact of water pollution incidences and prepare response systems for river environment safety for other water resources in the future. Environmental Fluid Dynamics Code (EFDC) was applied to the mainstream of the Yeongsan River where residential, commercial, and agricultural areas are located to analyze the behavior of pollutants conducting the scenario analysis. Considering the pollutants that affected the study area, two pollutants, oil and benzene, with different physical and chemical characteristics were selected for the analysis. As a result of comparing the actual and simulated values of the water elevation, temperature, and flow rate, it was confirmed that the model adequately reproduced the hydraulic characteristics of the Yeongsan River. The oil flow dynamics showed that an increase in flow rate led to reduction in the maximum height of the slick. Notably, the behavior of the oil was predominantly influenced by the wind conditions. In the case of benzene, lower flow scenarios exhibited decreased arrival times and residence times accompanied by an elevation in the maximum concentration levels. From the results of pollutant behavior in the study area, it is feasible to utilize the section of tributary confluence for collection and the weir area for dilution. This study enhances the understanding of the pollutant's behavior with different characteristics and develops effective control systems tailored to the physicochemical attributes of pollutants.

• Asian-Australasian Journal of Animal Sciences
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• v.9 no.6
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• pp.705-709
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• 1996

A simplified dilutor for cock spermatozoa at ambient temperature was achieved by adjusting the 5% concentration of fructose in isotonic saline. Motility of cock spermatozoa was arrested completely for maximum 6 hrs without affection the survivability of spermatozoa by employing this sugar. To study the effect of high concentration of fructose on fertility, sperm were inseminated with or without fructose at different hrs. Fructose from semen samples was removed by centrifugation. High fertility obtained in the hens inseminated with fructose free sperm (washed). In addition, washed sperm maintained the 85.00% fertility for 6 hrs in winter season ($17-21^{\circ}C$) and 82.67% fertility for 3 hrs in summer season ($31-35^{\circ}C$). Whereas control groups showed 47.33 and 25.33% fertility in winter and summer season respectively. No significant difference was found in percent motility and live counts between the control and washed experimental groups during winter season. However, these measures differed significantly in summer. Washing of cock spermatozoa more than once, high speed centrifugation and more duration for centrifugation proved harmful to fertility. It may be concluded that fructose (5%) can be used as a motility or metabolic inhibitor of spermatozoa for short-term storage of cock semen at ambient temperatures.

• KSBB Journal
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• v.14 no.5
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• pp.523-527
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• 1999

A naturally luminescent bacterium, Photobacterium phosphoreum was stored in 2.5% NaCl solution at 2$0^{\circ}C$, 4$^{\circ}C$, -2$0^{\circ}C$ and -7$0^{\circ}C$ for 30 days. In vivo luminescence and concentrations of total and culturable cells were determined by luminometer, spectrophotometer and dilution plate counting, respectively. When stored at 4$^{\circ}C$ and 2$0^{\circ}C$, concentrations of cells were rapidly decreased as a result of cell lysis, leading to adrop in turbidity and cultured counts. The bioluminescence of cells stored at 4$^{\circ}C$ was maintained until 12 days while those of cells starved at other temperatures decreased to background level within 3 days. Following incubation of stored cells in fresh liquid medium, activities of viable cells increased throughout storage period excepting cells stored at 2$0^{\circ}C$. Changes in bioluminescence intensity following addition of 2.5% NaCl solution markedly showed in cells stored at -2$0^{\circ}C$ and -7$0^{\circ}C$ and increased to maximum 8 fold.

• BMB Reports
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• v.32 no.6
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• pp.573-578
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• 1999

Treatment of Hafnia alvei aspartase with limited tryptic digestion resulted in a marked increase in enzymatic activity. The activation required a few minutes to attain maximum level and, thereafter, the activity gradually decreased to complete inactivation. The degree of cleavage associated with the activation was extremely small as judged by SDS-PAGE. Upon activation, the optimum pH and temperature were essentially unchanged. When trypsin-activated enzyme was denatured in 4 M guanidine-HCI followed by removal of the denaturant by dilution, the restoration of activity was similar (40%) to that of the native enzyme, indicating a degree of stability. The $pK_a$ obtained on the acidic side and the $pK_b$ obtained on the basic side of trypsin-activated aspartase were 6.6 and 8.6, respectively, the same as those of the native aspartase, indicating that aspartase may exist in a stable conformation after limited tryptic digestion. These results indicate that the activation of H. alvei may be mediated by a conformational change away from the active site of individual subunits.

• Journal of Microbiology and Biotechnology
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• v.16 no.12
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• pp.1947-1953
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• 2006

There have been a number of studies of methods for recycling animal wastewater to provide new bioresources. In the present work, a marine algal culture medium, designated KEP II, was prepared by adding swine waste (3% v/v) fermented by soil bacteria to a dilution of f/2 culture medium (CT). When Phaeodactylum tricornutum was grown in batch culture in KEP II, the cells lasted long at the exponential phase producing the specific growth rate and biomass; the production of total amino acids and secondary metabolites rose up to 5-fold. It also substantially enhanced the maximum quantum yield of photo system (PS) II of P. tricornutum, greatly increased the level of thylakoid membranes containing PS, and stimulated the production of pyrenoids, including enzymes for $CO_2$ fixation in chloroplasts. KEP II should improve the cost efficiency of industrial mass batch cultures and the value of microalgae for long-term preservation of fresh aquaculture feed as well as production of anticancer and antioxidant agents. Specifically, a low-cost medium for growing the diatoms of aquaculture feed will be economically advantageous.

• Microbiology and Biotechnology Letters
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• v.19 no.4
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• pp.419-427
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• 1991

Ethanol fermentation of glucose by a strain of Saccharomyces cereuisiae was studied in membrane recycle bioreactor, where the fermentation vessel was coupled with cross flow hollow fiber membrane. The cell recycle system controlled backflushing with fresh medium was proven to be effective in alleviating membrane fouling and allowing long term operation of high-cell continuous fermentation. Using 100 g/l initial glucose concentration, the maximum productivity of about 9 5 g/$l \cdot h$ has been achieved at dilution rate 2.5 $h^{-1}$ and bleed stream ratio 0.05 with the corresponding ethanol concentration of 35g/l and glucose conversion of 100%. Increasing the glucose concentration to 200 g/$l \cdot h$ resulted in an increase in ethanol concentration to 48 g/l and productivity to 120 g1l.h. Substrate conversion, however, was only 69%. This productivity was the highest value in the study, and about 38 fold more than that of batch culture and 17 fold more that of single stage continuous culture without cell recycling. No further increase in the productivity was obtained when the glucose concentration was increased reased to 300g/l.

• Journal of Microbiology and Biotechnology
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• v.8 no.1
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• pp.8-13
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• 1998

Animal cells in culture typically convert most of the glucose they consume into lactate. The accumulation of lactate, however, is commonly cited as one of the factors that inhibit cell growth and limit the maximum cell concentration that can be achieved in culture. The specific production of lactate and the amount of glucose converted to lactate can be reduced when cells are grown in a fed-batch culture in which the residual glucose concentration is maintained at low levels. Such a fed-batch culture was used to grow and adapt hybridoma cells into a low-lactate-producing state before changing into continuous culture. The cells reached and maintained a high viable cell concentration at steady state. In a similar manner, cells that were initially grown in batch culture and a glucose-rich environment reached a steady state with a cell concentration that is much lower. The feed composition and dilution rates for both cultures were similar, suggesting steady state multiplicity. From a processing perspective the desired steady state among those is the one with the least metabolite production. At such seady state nutrient concentration in the feed can be further increased to increase cell and product concentrations without causing the metabolite inhibitory effect typically seen in a cell culture. Controlling cell metabolism in a continuous culture to reduce or eliminate waste metabolite production may significantly improve the productivity of mammalian cell culture processes.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.237-240
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• 2000

Organic acids which were produced from biomass wastes streams by cell-recycle fermentation using Propionibacterium acidipropionici ATCC 4965 were extracted by Membrane Contactor using TOA/MIBK system. Maximum productivity was 3.32g organic acid/L/hr at the dilution rate of 0.2/hr in the results of continuous fermentation. The diluted organic acids in the fermenter were selectively separated by Membrane Contactor extraction using 30%(w/w) trioctylamine(TOA) dissolved in methylisobutylketone(MIBK). The flow rate of aqueous phase is 200ml/min and that of extraction phase is 100ml/min. The degree of Acetic acid and Propionic acid extraction from fermentation broth was reached 56.25%, 72.41% respectively.