• Journal of the Korean Mathematical Society
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• v.40 no.1
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• pp.87-107
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• 2003

In this paper, we consider a discrete time queueing system fed by a superposition of an ON and OFF source with heavy tail ON periods and geometric OFF periods and a D-BMAP (Discrete Batch Markovian Arrival Process). We study the tail behavior of the queue length distribution and both infinite and finite buffer systems are considered. In the infinite buffer case, we show that the asymptotic tail behavior of the queue length of the system is equivalent to that of the same queueing system with the D-BMAP being replaced by a batch renewal process. In the finite buffer case (of buffer size K), we derive upper and lower bounds of the asymptotic behavior of the loss probability as $K\;\longrightarrow\;\infty$.

• 한국생물공학회:학술대회논문집
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• 2002.04a
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• pp.157-160
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• 2002

Probiotics can form profitab1e microorganisms in human or animal internal organs. When it is fed at domastic animals, can bring the rise of weight and prevention of disease. Pichia anonwla by new probiotics have antibiotic effect and oder reducing effect. we researched about optimal condition of pilot scale fermentation and freezed dry of pichia anonwla.

• 한국생물공학회:학술대회논문집
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• 2002.04a
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• pp.184-187
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• 2002

Lovastatin is a cholesterol-lowering agent, which plays a role of an inhibitor of 3-hydroxy-3- methylglutaryl coenzyme A reductase (HMG-CoA). When thiamine was supplemented in 3L batch fermentation, the production of lovastatin was improved. At the same time, the levels of pyruvic acid and NAD(P)H were estimated in the course of the fermentation of A. terreus. For the high level production of lovastatin, semi fed-batch fermentation was performed. And the thiamine level was maintained to a concentration of 20 mg/L and glucose was supplied. The final dry cell weight was lowered by 30 % and final lovastatin concentration was increased by 33 %. Final lovastatin concentration of 3.3 g/L was achieved in 8 days.

• Journal of Microbiology and Biotechnology
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• v.16 no.2
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• pp.308-311
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• 2006

In an attempt to increase production of LK8, an 86-amino-acid kringle fragment of human apolipoprotein(a) with three disulfide linkages, protein disulfide isomerase (PDI) was coexpressed in recombinant Saccharomyces cerevisiae harboring the LK8 gene in the chromosome. Whereas overexpression of the LK8 gene without coexpressing PDI was detrimental to both host cell growth and LK8 production, coexpression of PDI increased the LK8 production level by 2.5-fold in batch cultivation and 5.0-fold in fed-batch cultivation compared with the control strain carrying only the genomic PDI gene.

• KSBB Journal
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• v.8 no.1
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• pp.28-35
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• 1993

The serum free medium was developed and used for the suspension culture of mammalian cells. Although there were the problems of the longer lag time and the smaller maximum cell concentration achievable, the higher specific productivity as well as other advantages of the serum free medium can make it a more realistic alternative. The existence of a staggering period in glucose concentration vs. time profile in the batch culture can be a practical indicating signal for performing fed batch culture. The concentration dependence of the effects of the additives in the serum free medium as well as its economic feasibility was also tested.

• Journal of Microbiology and Biotechnology
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• v.9 no.6
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• pp.789-793
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• 1999

The effect of acetic acid formation deficiency on recombinant E. coli fermentation was investigated using a mutant strain deficient in acetic acid formation. A mutant strain which does not grow under anaerobic conditions was isolated. The acetic acid production in this strain was negligible in aerobic batch fermentation. The cloned-gene expression in the mutant strain was higher than the wild-type strain. Fed-batch fermentations with controlled specific growth rates were carried out in order to compare the cloned-gene expression between the wild-type and the mutant strains. The expression decreased along with the specific growth rate in both strains. The cloned-gene expression in the mutant strain was 60% higher than in the wild-type strain at the same specific growth rate.

• Microbiology and Biotechnology Letters
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• v.32 no.2
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• pp.135-141
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• 2004

Human granulocyte colony-stimulating factor (hG-CSF) is a hematopoiesis agent that principally affects the differentiation of neutrophils in the bone marrow. At present, recombinant hG-CSF is used successfully in the treatment of chemotheraphy-induced neutropenia and its indication has been expanded to bone marrow transplantation and aplastic anemia. In this study, we have constructed rhG-CSF secretion plasmid pYRC1 in which OmpA signal sequence/hG-CSF gene was expressed under the control of the T7 promoter. rhG-CSF produced in E. coli BL21 (pYRC1) grown at $37{\circ}C$ was found in aggregates. However, 15% of the periplasmic protein was soluble rhG-CSF when the E. coli BL21 (pYRC1) was cultured at $25^{\circ}C$ for 7 h in the modified MBL medium containing 10 g/$\ell$ glucose with 10 $\mu$M IPTG induction. The production of soluble rhG-CSF in E. coli BL21 (pYRC1) using fed batch culture was also studied. In the fed batch culture system, the final yield of rhG-CSF produced from E. coli BL21 (pYRC1) was increased from 4.4 mg/$\ell$to 24 mg/$\ell$by controlling the specific growth rate from $0.43 h^{-1}$ to $0.14 h^{-1}$, and optimizing the time of induction.

• KSBB Journal
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• v.17 no.1
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• pp.93-99
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• 2002

Two-stage fed-batch culture of Candide tropicalis that was designated primarily to cultivate the cell in the glucose medium (1st stage) and then produced the xylitol from xylose medium (2nd stage) was developed to improve a xylitol yield and productivity. In the growth stage, glucose was automatically supplied to the fermentor by pH-stat mode when the pH was up 5.7, When a feeding medium was added in order to reach the glucose and yeast extract concentrations up to 100 and 40 g/L, respectively, a high cell concentration and a relatively low ethanol concentration were obtained in 18.5 h culture. In the production stage, initial xylose concentration of 150 g/L was the most favorable for obtaining the final xylitol concentration and productivity. The addition of mineral salts was also enhanced a xylitol production. But the aeration rate was not significantly affected a xylitol production. When the addition of 16 g yeast extract and 232.5 g xylose powder at the production stage was used, xylitol yield and productivity were significantly increased. With these conditions, xylitol concentration, yield and productivity of 108.9 g/L, 74%) and 3.3 g/L·h, respectively, were obtained in a final volume of 1.58 L. The further addition of 16 g yeast extract and 232.5 g xylose powder increased the working volume partly (1.67 L) and resulted in a relatively high xylitol concentration, yield and productivity of 193 g/L, 70% and 3.6 g/L·h, respectively.

• KSBB Journal
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• v.21 no.2
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• pp.79-84
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• 2006

In order to minimize the reduction of lysine productivity by accumulation of lysine and byproducts in the end of fed-batch fermentations, a salt-tolerant mutant C14-49-3-15-7-3-20, which could grow at high concentrations of NaCl was isolated through mutagenesis from the Corynebacterium glutamicum mother strain I. In the evaluation of L-lysine productivity by fed-batch fermentations using a 5 L jar fermenter, the salt-tolerant mutant strain C14-49-3-15-7-3-20 produced 130.6 g/L of L-lysine with a 48.6% of yield. The mother strain I produced L-lysine concentration only 104.9 g/L with a yield 41.8%, implying the improvement of L-lysine productivity by introduction of salt-tolerance character.

• Korean Journal of Food Science and Technology
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• v.28 no.1
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• pp.122-126
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• 1996

Growth patterns of Saccharomyces cerevisiae NS 2031 and its total RNA contents were observed by a fed-batch fermentation with different media-feeding methods. With an exponential feeding pattern, both final cell concentrations and intracellular RNA contents decreased with increasing feeding rates. Intracellular RNA contents also decreased with the growth time. At the same feeding rate of the exponential pattern, final cell concentrations decreased with the increase of total sugar concentration whereas intracellular RNA contents increased. The highest cellular yield was 0.47 at the total sugar concentration of 10%. With increasing feeding rates of the parabolic feeding pattern, final cell concentrations decreased whereas intracellular RNA contents increased, showing a different tendency from the exponential feeding pattern. In comparison of two feeding methods, the exponential feeding pattern was better than the parabolic feeding pattern in terms of cell growth, cellular yields and intracellular RNA contents of Saccharomyces cerevisiae NS 2031. Also, the intracellular RNA contents of the exponential feeding pattern was found to be about 2% higher than that of the parabolic feeding pattern at the same instantaneous growth rate $({\mu}_{inst})$.