• Microbiology and Biotechnology Letters
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• v.23 no.5
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• pp.588-592
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• 1995

Fed-batch fermentation was used to produce the high concentrations of poly-$\beta $-hydroxybutyrate (PHB) and poly-$\beta $-(hydroxybutyrate-co-hydroxyvalerate) (PHB/V). Specific growth rate ($\mu $), yield of cell from glucose (Y$_{x/s}$) were calculated from the two samples in 3 to 5 hours of interval and they were reflected on the determination of glucose feeding rate to maintain the glucose concentration at around 10 g/l in the culture broth. PHB was accumulated after the nitrogen became limited at 60 g/l of dry cell weight by changing ammonia water to 4N-NaOH solution. As results, the final dry cell weight (DCW) of 170 g/l, PHB of 115 g/l were obtained in 50 hours and the overall productivity was 2.4 g/l$\cdot $h. After PHB accumulation, cosubstrate of glucose and propionic acid (PA) was fed to accumulate PHB/V. But, PA feeding rate was decreased from 3 g/l$\cdot $h to 1 g/l$\cdot $h to prevent PA from accumulating to high level in the broth, which is very inhibitory to the cells. As results, DCW, PHB and PHV were 147.5 g/l, 90 g/l and 8 mole % of hydroxyvalerate, respectively.

• Journal of Biomedical Engineering Research
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• v.10 no.2
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• pp.195-202
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• 1989

Chinese Hamster Ovary( CHO) cells were cultured on the surface-modified polymers described in the previous study( "Polymer Surfaces for Cell Adhesion. 1. Surface Modification of Polymers and ESCA Analysis, " J. of KOSOMBE, Vol. 10, No. 1, 43-51, 1989). Among the physicochemical treatment methods. the chloric acid treatment was found to be the best method of rendering the polymer surfaces adhesive for CHO cells probably due to the high density of hydroxyl groups on the surface. Among the biological methods, the fibronectin treatment was best for CHO cell-compatibility probably due to specific active sites existed on the tell-binding domains of the fibronectin structure. When we compare the cell-compatibility of the chloric acid - and the fibronectin -treated PET surfaces, the number of cells attached on the surfaces were increased by 460.5 % and 559.0 % and, respectively, after 32 hr CHO cell culture, compared to that of untreated PET.eated PET.

• International Journal of Industrial Entomology and Biomaterials
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• v.9 no.2
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• pp.173-181
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• 2004

To delay the onset of apoptosis in the culture, transformed Tn 5B1-4 cells harboring anti-apoptotic genes, bcl-2 and baculovirus p35, have been established and analyzed for their anti-apoptotic ability in suspension culture using spinner flasks. In the suspension culture at agitation speeds of 100 rpm and 200 rpm, the cell growth of cell clone expressing Bcl-2 protein was much higher than other two clones and the maximum cell density of the clone was 6.0 ${\times}$ 10$^{6}$ cells/ml and 6.2 ${\times}$ 10$^{6}$ cells/ml at day three of the incubation. On the other hand, the cell growth of cell clone expressing baculovirus protein P35 was much higher than other two clones in suspension culture at agitation speed of 300 rpm and the maximum cell density of the clone was 6.1 ${\times}$ 10$^{6}$ cells/ml at day three of the incubation. Based on the pattern of genomic DNA laddering and the microscopic observation of apoptotic bodies, the more apoptotic bodies are induced in Tn 5B1-4 control cell clone at higher agitation speed. This result shows that the shear stress can be a main factor in inducing apoptosis in spinner flask culture. At low agitation speed, cell clone expressing Bcl-2 was more effective in delaying the onset of apoptosis than the cell clone expressing P35. On the other hand, at high agitation speed, cell clones expressing baculovirus P35 was more effective in delaying the onset of apoptosis than the cell clone expressing Bcl-2. Therefore, anti-apoptotic genes, bcl-2 and baculovirus p35, can playa distinct role depending on agitation speed in the suspension culture.

• Biotechnology and Bioprocess Engineering:BBE
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• v.5 no.3
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• pp.207-210
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• 2000

When endothelial cells isolated isolated from human umbilical venis were cultred for 6dary using 96-well microplates, the final cell density in each was fiund not to be the same although the medium composition of each well was exactly the same. Cell growth in the wells located at the periphery of a microplate was low, while that in the central area of the plate was high. A possible cause for different rate of growth was proposed as the uneven concentration of oxygen in the culture medium of each well.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.428-432
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• 2003

In this study, we demonstrated that high cell density for Thiobacillus ferrooxidans could be obtained when optimal conditions for cell growth were maintained using electrochemical cultivation with sufficient aeration. The optimal pH for cultivation were determined to be $2.0{\pm}0.05$. When the current and potential were set to 0.15A, 4V, the Pt electrode reduced $Fe^{3+}$ to $Fe^{2+}$ with efficiency of 85%. Under these condition, cells at an initial density of 0.0025 g-dry cell/L grew for 8days until the cell density was 0.0576 g-dry cell/L. this was a 7-fold increase over conventional batch culture.

• Microbiology and Biotechnology Letters
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• v.30 no.1
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• pp.63-67
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• 2002

Bifidobacterium strain was isolated from the feces of brast fed infants. The isolated strain was identified as Bifidobacterium longum by 16S rRNA sequence analysis and named as Bifidobacterium SH2. The MRS medium was modified to obtain high density cells of Bifidobacterium SH2. The optimal medium was determined to be 50 g/L lactose, 10 g/L beef extract, 10 g/L peptone, 5 g/L yeast extract, 7 g/L sodium acetate, 2 g/L ammonium citrate, 2 g/L disodium phosphate,1 g/L tween 80, 0.2 g/L MnSO$_4$ and 0.5 g/L L-cysteine. The pH and temperature were optimized as 5.0 and $37^{\circ}C$, respectively. Through out the optimization of medium composition and culture conditions, the dry cell weight and viable cell count were 2.5 times and 1.8 times higer than those in MRS medium, respectively.

• Journal of Microbiology and Biotechnology
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• v.18 no.7
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• pp.1252-1256
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• 2008

Cell recycled culture of succinic acid-producing Anaerobiospirillum succiniciproducens was anaerobically carried out using an internal membrane filter module in order to examine the physiological response of A. succiniciproducens to a high-cell-density environment. The optimal growth of A. succiniciproducens and its enhanced succinic acid productivity were observed under $CO_2$-rich conditions, established by adding $NaHCO_3$ and $Na_2CO_3$, in the cell recycled system. A. succiniciproducens grew up to 6.50 g-DCW/l, the highest cell concentration obtained so far, in cell recycled cultures. The cells did not change their morphology, which is known to be easily changed in unfavorable or stress environments. The maximum productivity of succinic acid was about 3.3 g/l/h, which is 3.3 times higher than those obtained in batch cultures. These results can serve as a guide for designing highly efficient cell recycled systems for succinic acid at a commercial level.

• 한국생물공학회:학술대회논문집
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• 2005.04a
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• pp.37-37
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• 2005

Human chorionic gonadotropin (hCG) is a heterodimeric glycoprotein hormone consisting of non-covalently linked two subunits, the ${\alpha}$ and ${\beta}$ subunit. It has been used as a infertility drug for ovulation to mimic luteinizing hormone $(LH).^{1)}$ A stable cell line was established by transfection of Rc/CMV-i-dhfr-hCG, expression vector containing hCG ${\alpha}-$ and ${\beta}-genes$, into dihydrofolate reductase-deficient CHO cells and subesquent methotrexate-mediated gene amplification. Anchorage-dependent CHO cells were adapted into a serum-free and/or animal component-free suspension medium through gradual serum weaning for the hCG production. The established cell line showed typical morphological characteristics and growth profile of CHO cells, and could produce FSH with passage-to-passage consistency. The high density perfusion culture of the CHO cells was carried out in Celligen Plus bioreactor equipped with a spin-filter as a internal cell retention device. The cell density reached up to $>1x10^{7}$ cells/ml in less than 7 days and a perfusion-control strategy based on cellular consumption rates of glucose was $established.^{2)}$ Biologically active recombinant hCG was purified by a series of chromatographic steps including anion exchange chromatography and hydrophobic interaction chromatography to homogeneity. The highly purified recombinant hCG was characterized for physicochemical, immunological and biological properties.

• Korean Journal of Microbiology
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• v.35 no.4
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• pp.302-306
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• 1999

Production of biomass by fed-batch culture of Saccharomyces cerevisiae Hansen CBS5926, which is used to treat intestinal disorders, was investigated using ethanol as the sole carbon source. Ethanol was a better carbon source than glucose for high cell density culture of the st-rain since it could decrease the frequency of contamination while increasing the efficiency and final productivity of the fermentation process. Under optimal conditions, 38 g/ℓ of dry cell weight with $2.2{\times}10^{9}$ cfu/㎖ of maximum viable cell count was achieved after 72h cultivation. Freeze-drying of the cultured yeast cells resulted in severe reduction of viability. Of the freeze-drying protectants tested, 20% sucrose and 30% lactose were most effective for the preservation of yeast cells with a viability level of 16.3%. A combination of skim milk and lactose with 20% sucrose(w/v) exerted no synergistic influence upo the viability of the cells during cryopreservation by freeze-drying.

• Microbiology and Biotechnology Letters
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• v.30 no.1
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• pp.68-72
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• 2002

To obtain a yeast mutant with high RNA content and high growth rate, Saccharomyces cerevisiae MTY62 was mutated with ethylmethane sulfonate. Among the selected mutants that were sensitive to the high concentration of KCl, M40-10 strain was finally selected due to its rapid cell growth and high RNA content in the tube and baffled-flask cultures. In the batch culture of M40-10 mutant, the maximum specific growth rate ($\mu_{max}$) of $0.38 h^{-1}$ , RNA concentration of 3210 mg-RNA/1, and RNA content of 183 mg-RNA/g-DCW were obtained, which were 23%, 15%, and 12% increased levels, respectively, compared to those of MTY62 parent strain. The intermittent fed-batch culture of M40-10 strain resulted in the maximum cell concentration of 35.6 g-DCW/1, RNA concentration of 5677 mg/1, and RNA content of 160 mg-RNA/g-DCW. Through the constant fed-batch culture, the maximum cell concentration of 46.4 g-DCW/1, RNA concentration of 6270 mg-RNA/1, and RNA content of 135 mg-RNA/g-DCW were obtained. At the 20 h culture time in the fed-batch cultures of M40-10 strain, the cell and RNA concentrations were increased by 30% and 10%, respectively, over the parent strain MTY62. In addition, it was also found that the accumulated RNA within the mutant cell was not degraded until the end of fed-batch cultivation, indicating that the M40-10 cell is a mutant with weak acidic RNase activity.y.