• Biotechnology and Bioprocess Engineering:BBE
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• 제7권2호
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• pp.117-120
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• 2002

The effect of cell density on cell growth was investigated in a suspension batch culture of hybridoma cells. The specific growth rate was found to increase with increasing initial cell density and then to decrease with further increases in initial cell density. In order to quantitatively describe the dependence of specific growth rate on cell density, a kinetic model is proposed, which satisfactorily represents the experimental data.

• 한국수소및신에너지학회논문집
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• 제32권5호
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• pp.410-416
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• 2021

The initial electrochemical performance of ceramic fuel cell with thin-film electrolyte was evaluated in terms of peak power density ratio, open circuit voltage ratio, and activation/ohmic resistance ratios at 500℃. Hydrogen and air were used as anode fuel and cathode fuel, respectively. The peak power density ratio reduced as ~17% for 40 minutes, which rapidly decreased in the early stage of the performance evaluation but gradually decreased. The open circuit voltage ratio decreased with respect time; however, its time behavior was remarkably different with the reduction behavior of the peak power density ratio. The activation resistance ratio increased as ~15% for 40 minutes, which was almost similar with the time behavior of the peak power density ratio.

• 한국수소및신에너지학회논문집
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• 제32권5호
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• pp.340-346
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• 2021

The initial electrochemical performance of ceramic fuel cell with thin-film electrolyte fabricated by plasma-enhanced atomic layer deposition method was evaluated in terms of peak power density ratio, open circuit voltage ratio, and activation/ohmic resistance ratios at 500℃. Hydrogen and air were used as anode fuel and cathode fuel, respectively. The peak power density ratio reduced as ~52% for 30 min, which continually decreased as time increased but degradation rate gradually decreased. The open circuit voltage ratio decreased with respect time; however, its behavior was evidently different from the reduction behavior of the peak power density. The activation resistance ratio increased as ~127% for 30 min, which was almost similar with the reduction behavior of the peak power density ratio.

• Journal of Microbiology and Biotechnology
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• 제23권4호
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• pp.539-544
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• 2013

The effects of culture depth (2-10 cm) and cell density on the growth rate and biomass productivity of Chlorella sp. XQ-200419 were investigated through the use of a self-designed open circular pond photobioreactor-imitation system. With increases in culture depths from 2 to 10 cm, the growth rate decreased significantly from 1.08 /d to 0.39 /d. However, the biomass productivity only increased slightly from 8.41 to 11.22 $g/m^2/d$. The biomass productivity (11.08 $g/m^2/d$) achieved in 4 cm culture with an initial $OD_{540}$ of 0.95 was similar to that achieved in 10 cm culture with an initial $OD_{540}$ of 0.5. In addition, the duration of maximal areal productivity at a 4 cm depth was prolonged from 1 to 4 days, a finding that was also similar to that of the culture at a 10 cm depth. In both cases, the initial areal biomass densities were identical. Based on these results and previous studies, it can be concluded that the influence of culture depth and cell density on areal biomass productivity is actually due to different areal biomass densities. Under suitable conditions, there are a range of optimal biomass densities, and areal biomass productivity reaches its maximum when the biomass density is within these optimal ranges. Otherwise, biomass productivity will decrease. Therefore, a key factor for high biomass productivity is to maintain an optimal biomass density.

• KSBB Journal
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• 제13권3호
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• pp.272-278
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• 1998

Cell recovery from high cell density broths of Alcaligenes eutrophus by pretreatment with aluminum-based coagulants such as aluminum sulfate, polyaluminum hydrooxide chloride silicate (PACS), and polyaluminum hydrooxide chloride (Hi-PAX) was carried out. Cells coagulated with coagulants could be successfully recovered above 95-99% by centrifugation or filtration. The optimum initial pH of fermentation broths for cell recovery was in the range of 10 to 12. Optimum coagulants dosage for cell recovery increased with increasing of cell concentrations (21-160 g/L). The optimum coagulant dosages to recover cells with more than 95% cell recovery by centrifugation for the cell concentrations ranged 21-160 g/L were as follows: aluminum sulfate, 416-1708 mg Al/L; PACS, 211-826 mg Al/L; Hi-PAX, 320-960 mg Al/L. At optimum conditions for the coagulation of cells, centrifugal forces for 95% of cell recovery were dependent on the cell concentration. The centrifugal forces at 82 g/L and 160 g/L of cell concentration were only 45${\times}$g and 1600${\times}$g, respectively.

• Biotechnology and Bioprocess Engineering:BBE
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• 제5권5호
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• pp.350-354
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• 2000

The growth promotion of a Taxus brevifolia cell suspension culture was investigated using conditioning factors. The conditioning factors produced and secreted from cultured cells usually stimulate cell division and the production of secondary metabolites. Therefore, the effective incubation time for the optimal secretion of conditioning factors was firstly determined for the promotion of cell growth. Conditioned media obtained by cultivating for 2 and 5 days showed the promotion of initial cell growth during the early cell growth period. However, the positive effect of the conditioning factors on the initial cell growth did not continue because of the depletion of the medium nutrients. Accordingly, the addition of a carbon source to the conditioned medium prolonged the positive effect on the cell growth. The addition of sucrose to the conditioned medium resulted in the maximum cell density being reached 4 days earlier compared to the control group and an increased substrate yield.

• KSBB Journal
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• 제9권4호
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• pp.428-435
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• 1994

탄소원으로 초기 glucose 농도와 초기 maltose 농도를 5g/$\ell$, 109/$\ell$, 20g/$\ell$ 로 한 후 Bacillus a amyloliquefaciens(ATCC 23350 ) 균주를 이용하여 플라스크 배양시의 세포 성장과 생성물 생성에 대한 연구를 수행하였다. 균주의 최대 건조세포농도는 초기 maltose 농도가 증가할수록 증가하였으나, glu­c cose에서는 초기 농도가 109/$\ell$일 때 가장 높았다 최대 비성장속도는 초기 glucose농-토가 109/$\ell$ 일 때 $0.060(hr^{-1})$로 가장 높으며, maltose에서는 초기 농도가 5g/P 얼 때 $0.042(hr^{-1})$이였다. 균주에 의해 생성되는 최대 a-amylase 생산은 초기 maltose 농도가 109/P 얼 때 l49.0unit/ml로 가장 높았으며, 초기 maltose 농도가 증가할수록 증가하였다. 최대 비생성속도는 초기 maltose 농도가 5g/$\ell$ 일 때 3.26unit/ mg- hr로 가장 높았으며 , glucose보다는 maltose에서 더 높았다. 균주에 의해 생성되는 최대 ${\alpha}$-acetic acid는 탄소원의 초기 농도가 증가함에 따라 감소하며, 초기 glucose 농도 109/$\ell$ 일 때 0.94g/$\ell$ 로 가장 많이 생성되였고, lactic acid는 탄소원의 초 기 농도가 증가할수록 증가하였으며, 초기 maltose 농도가 20g/$\ell$일얼 때 8.20g/$\ell$ 로 가장 많이 생성되였 다.

• KSBB Journal
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• 제11권3호
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• pp.303-310
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• 1996

해양 미세조류인 Isochrysis galbana Parke의 성장에 미치는 여러 환경요인과 배지요인의 영향을 조사하고 최적 배양조건을 구하였다. 그 결과를 요약하 면 다음과 같다. 1. 인공바닷물은 자연바닷물보다 다소 낮은 비성 장속도와 최종 균체농도를 나타내었다. 2.. 자연바닷물이 기초배지로 사용되었을 때 2mM 이상의 충분한 질산염 농도가 필요하였다. 그러나 미량원소와 비타민의 영향은 관찰되지 않았다. 3. 완충용액요로 Tris를 첨가한 경우 pH는 일정 하게 유지가 가능하나 비성장속도와 최종 균체농도 가 감소하였다. 4. 최적 초기 pH와 온도는 각각 pH 8, $20^{\circ}C$ 였다. 5. 벚세기를 400-21001ux의 범위에셔 변화시켰을 때 비성장속도는 18501ux까지 증가하였고 그 이 후로는 일정하였다. 6. 10mL에서 70mL로 Working volume을 증가 시켰을 때 초기 성장속도는 비슷하였으나 최종 균체 농도가 감소하는 경향을 보였다. 7. Working volume이 30mL일 때 최적 교반속 도는 100rpm정도이고, 더 높은 교반속도에서는 최 종 균체농도의 감소가 관찰되었다. 8. 플라스크배양의 최적조건에서 최대 비성장속도 와 최종 균체농도는 각각 $O.021hr^{-1}$과 1.1g/L로 얻어졌다.

• KSBB Journal
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• 제13권2호
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• pp.187-194
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• 1998

For mass production of polyhydroxyalkanoates (PHA), high cell density cultures of Alcaligenes eutrophus by fed-batch culture under phosphate-limitation condition has been investigated. PHA accumulation by the regulation by the regulation of initial phosphate concentration could be automatically induced, and high density cell culture above 200 g/L also could be successfully produced. The production of Poly-$\beta$-hydroxybutyrate (PHB) and dry cell weight increased with increasing the initial phosphate concentration. When the initial concentrations of phosphate were in the ranges of 1.5~4.5 g-PO$_4$/L, PHB and dry cell weight obtained were 83~266 g/L and 61~216 g/L, respectively, and PHB productivity was in the ranges of 1.35~3.10 g/L.h. When a mixture of glucose and propionic acid is used as carbon sources, poly(3-hydroxybutyrate-co-poly-3-hydroxyvalerate), P(3HB-co-3HV), could be also successfully produced under phosphate limitation condition. When the mole ratio of propionic acid to glucose in the feeding solution is 0.22, a final dry cell weight of 150 g/L and a P(3-HB-co-3HV) of 90 g/L were produced. Morphological changes and size distribution of PHB granules synthesized in A. eutrophus under phosphate-limitation condition are determined by TEM during the course of fed-batch. Mean granule diameters of PHB produced are in the range of 0.36~0.39 $\mu$m, and mean cell size was elongated from 0.54~0.59 $\mu$m$\times$ 1.3~1.5 $\mu$m to 0.83~0.89 $\mu$m $\times$2.0~2.3 $\mu$m. Phosphate concentration in media did not affect size distribution of PHB granule and cell.

• ALGAE
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• 제28권2호
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• pp.193-202
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• 2013

Nitrogen availability and cell density each affects growth and cellular astaxanthin content of Haematococcus pluvialis, but possible combined effects of these two factors on the content and productivity of astaxanthin, especially under outdoor culture conditions, is less understood. In this study, the effects of the initial biomass densities IBDs of 0.1, 0.5, 0.8, 1.5, 2.7, 3.5, and 5.0 g $L^{-1}$ DW and initial nitrogen concentrations of 0, 4.4, 8.8, and 17.6 mM nitrate on growth and cellular astaxanthin content of H. pluvialis Flotow K-0084 were investigated in outdoor glass column photobioreactors in a batch culture mode. A low IBD of 0.1 g $L^{-1}$ DW led to photo-bleaching of the culture within 1-2 days. When the IBD was 0.5 g $L^{-1}$ and above, the rate at which the increase in biomass density and the astaxanthin content on a per cell basis was higher at lower IBD. When the IBD was optimal (i.e., 0.8 g $L^{-1}$), the maximum astaxanthin content of 3.8% of DW was obtained in the absence of nitrogen, whereas the maximum astaxanthin productivity of 16.0 mg $L^{-1}\;d^{-1}$ was obtained in the same IBD culture containing 4.4 mM nitrogen. The strategies for achieving maximum Haematococcus biomass productivity and for maximum cellular astaxanthin content are discussed.