• Journal of the Korean Chemical Society
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• v.15 no.2
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• pp.95-105
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• 1971

The apparent molal volumes ${\phi}_v$ of a series of homologous tetraalkylammonium chlorides, $Me_4NCl, Et_4NCl, Pr_4NCl,\;and\;Bu_4NCl$, in a series of isopropanol-water mixtures have been determined at $30^{\circ}C$ from precision density measurements using pycnometers. The values of ${\phi}_v$ extrapolated to infinite dilution give partial molal volumes $\={V}^{\circ}$s which are almost additive for successive homologues and enable one to determine the absolute individual ionic partial molal volumes. The experimental results are discussed in terrns of the varying size and surface charge of the ions and the structure of the binary solvent mixtures. The results indicate that at 0.1 mole fraction isopropanol the maximum structuredness of water causes a minimum in the tetraalkylammonium-cation partial molal volumes, while at 0.2 mole fraction the solvent structure is such that the free volumes is a minimum and the electrostrictive effect of chloride ion is a maximum.

• KSBB Journal
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• v.13 no.4
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• pp.456-460
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• 1998

Fed-batch fermentations were carried out in order to improve the efficiency of hirudin production by recombinant Saccharomyces cerevisiae. A fed-batch fermentation done with the optimized semi-synthetic medium resulted in a maximum hirudin concentration of 342mg/$\ell$ by keeping a galactose concentrations between 10 and 30g/$\ell$ which corresponded to a 11.4-fold increase in hirudin concentration compared with the simple bach fermentation done with the same medium. Comparison of the chromatographic pattern of proteins in the growth medium clearly showed that the use of the semi-synthetic medium is more advantageous for separation of hirudin than the case o fusing the complex medium. Continuous cell recycle fermentation done at dilution rate of 0.1h-1 and an inlet galactose concentration of 100g/$\ell$ yielded a maximum hirudin productivity of 19.1mg hirudin/$\ell$$.$h.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 1979.04a
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• pp.115.2-115
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• 1979

By employing a two-stage continuous culture system, some of important physiological parameters involved in cellulase bicsynthesis have been evalua-ted with an ultimate objective of detigning an op-timally controlled tellulase process. Volumetric and specific cellulase productivities obtained were 90 IU/liter/hr and 8IU/g biomass/hr respectively. The maximum specific enzyme productivity observed was 14.8 IU/g hiomass/hr. The optimal dilution rate in the second stage which corresponded to the maximum enzyme productivity was 0.026-0.028 hr$^{-1}$ , and the specific growth rate in the second stage ihat suported maximum specific enzyme productivity was equal to orslightly less than zero. The maintenance coefficients deter-mined for oxygen and for carbon source are M$_{o}$=0.85mmmole/g biomass/hr and M$_{c}$=0.14 mmole hexose/g bio mass/hr respectively. The yield constants determined are; Y(x/o) =32.3g biomass/mole oxygen, Y (x/c) =1.1g bio-mass/g carbon or 0.44g biomass/g hexose, Y(x/n) = 19.6g biomass/g nitrogen for the enzyme produc-tion stage and 12.5g biomass/g nitrogen for the cell growth stage.e.e.

• Microbiology and Biotechnology Letters
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• v.25 no.3
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• pp.235-239
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• 1997

Chlorococcum littorale has been grown in high $CO_2$ concentrations to utilize $CO_2$ gas in the polluted air. The effect of incident light intensity on the specific growth rate is expressed by a photoinhibition model, showing half- saturation constant, $K_0\;as\;8\;(W/m^2)$ and inhibition constant, Ki as 35 $(W/m^2)$. The maximum specific growth rate was also estimated as 0.095 (1/day) under this condition. This strain maintained the optimum growth rate in 20% of $CO_2$ gas but 50% of input $CO_2$ gas is the maximum concentration considering the economical efficiency. The maximum Specific $CO_2$ consumption rate, $qCO_2$ was measured as 17.48 (mg $CO_2/g$ dry wt./day) in batch cultivation, 11.2 (mg $CO_2/g$ dry wt./day) in fed-batch cultivation and 10.87 (mg $CO_2/g$ dry wt./day) at 0.065 (1/day) of dilution rate in continuous cultivation. The chemical composition of the biomass obtained from this process showed 32.5% of protein, 27.5% of lipid, 16.5% of carbohydrate and ash 11.7%.

• KSBB Journal
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• v.13 no.4
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• pp.411-417
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• 1998

The possibility of application of membrane type immobilized adsorbent to the fed-batch or perfusion culture system with anchorage-independent cells as well as batch system was investigated. The improvement in cell density and cell viability due to the combination of immobilized adsorbent with each culture system was evaluated for the investigation, and the optimum culture system employing immobilized adsorbent system was suggested based on the results. It was observed that the system with immobilized adsorbent showed better cell growth and cell viability than that without immobilized adsorbent in every operation system of batch, fed-batch, and perfusion. In case of batch system, 200% improvement of maximum cell density was observed in the system where ammonium chloride was added on purpose. And 50% improvement of maximum cell density was observed in the fed-batch system where ammonium ion accumulates significantly, while small increase in maximum cell density was observed in the perfusion system where dilution of waste byproducts exists. Especially, the fed-batch system showed the most significant improvement on cell growth because both compensation of nutrient and removal of ammonium ion occurred simultaneously in the system. Therefore a combined system of immobilized adsorbent and fed-batch operation could be suggested as an optimum system with in situ removal of ammonium ion.

• Microbiology and Biotechnology Letters
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• v.48 no.4
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• pp.525-532
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• 2020

A continuous fermentation process was carried out to enhance hyaluronic acid (HA) production using Streptococcus zooepidemicus cells. During the 1st stage continuous operation from 8 h with a dilution rate of 0.029/h (D1), HA was produced in the range of 7.5-10 g/l. During the 2nd stage from 44 h with a dilution rate of 0.036/h (D2), HA production (8.28 g/l) was initially reduced to a small extent due to increase of dilution rate from D1 to D2, and then a new pseudo-steady state was formed within a few hours with a concurrent small variations of HA production. The HA amount produced during the latter part of the 2nd stage was stably maintained in the range of 8.28-9.48 g/l, about 4.7% less amount compared to the 1st stage. Due to 24% increase of dilution rate from D1 to D2, however, maximum volumetric productivity (DP) amounting to 0.341 g/l/h was obtained at 96 h during the 2nd stage. This maximum productivity obtained from the continuous culture turned out only a small increase (3%) as compared to the corresponding batch fermentation. However, it should be noted that, in the case of batch process, one run typically consists of serial stages of growth culture plus one final production culture. This implies that, if the continuous fermentation that practically needs no dead time necessary for the multi-stage growth cultures is run for longer period, the total amount of the accumulated HA would be far greater than the amount obtained from the corresponding batch culture performed for the identical period.

• Journal of Magnetics
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• v.21 no.1
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• pp.115-124
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• 2016

The present study analyzes T1 TSE and T1 slice sel. IR (dark_fluid) signal strength according to the degree of gadolinium contrast agent dilution and analyzes the turbo factors with regard to changes in the maximum and overall signal strength to study correlations between changes and signal-to-noise ratios (SNRs) and compare peak-to-peak SNR (PSNR) enhancement in order to improve the quality of T1-weighted images. Enhancement TR (600 msec) evaluated to determine the T1 TSE turbo factor and obtain the maximum signal strength, T1WI were used sequentially to experiment with turbo factors_1-4. T1 slice sel. IR (dark-fluid) was used to sequentially test turbo factors_2-5 but not turbo factor_1 at a TR (1500 msec) and compare data at an increase in T1 of 900 msec. The T1 TSE was reduced according to the contrast agent concentration. Phantom signal strength increased, whereas turbo factors_1-4 exhibited maximum signal strength at a concentration of 3 mmol, followed by a gradual decrease. In the turbo factors_2-5, the signal strength increased sharply to maximum signal strength at 0.7 mmol, followed by a reduction. T1 TSE had a greater maximum signal strength than did T1 slice sel. IR (dark_fluid). A comparison of SNR found that T1 TSE imaging was superior (33.3 dB) in turbo factor_1 and T1 slice sel. IR (dark_fluid) was highest (33.9 dB) at turbo factor_5. A PSNR comparison analysis was not sufficient to distinguish between the images obtained with both techniques at 30 dB or higher under all experimental conditions.

• KSBB Journal
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• v.5 no.4
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• pp.355-363
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• 1990

Methanol-utilizing bacterium isolated from sewage samples in Seoul showed optimal temperature and pH of $33^{\circ}C$ and 7.1 for growth, respectively. The maximum specific growth rate was $0.42hr^{-1}$. The minimum medium composition was reconstituted depending on the surplus and the deficit of each component in the basal medium at steady state. The optimal composition was given as(g/l); Methanol 40, $(NH_4)_2\;SO_42, \;KH_2PO_4\;1.5, \;K_2HPO_4\;0.2, \;H_3PO_4\;0.79, \;Na_2HPO_4{\cdot}12H_2O\;0.15, \;MgSO_4{\cdot}7H_2O\;1.5, \;FeSO_4{\cdot}7H_2O\;0.034, \;MnSO_4{\cdot}4H_2O\;0.005, \;CuSO_4{\cdot}5H_2O\;0.0027, \;CaCl_2{\cdot}2H_2O\;0.25, \;ZnSO_4{\cdot}7H_2O\;0.007, \;(NH_4)_6\;Mo_7O_{24}{\cdot}4H_2O\;0.00048, \;H_3BO_3\;0.00068, \;CoCl_2\; 0.00024$ Under the continuous culture with optimum medium the maximum cell productivity was 3.8g/1/hr at dilution rate $0.23hr^{-1}$. Maximum cell concentration and its protein content were 19.5g/l and 70% at dilution rate of $0.1hr^{-1}$, respectively.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.121-124
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• 2000

Organic acids were produced from wastes streams in food industries by cell-recycle fermentation using Propionibacterium acidipropionici ATCC 4965. As a results of continuous fermentation, maximum productivity was 3.32g organic acid/L/hr at the dilution rate of 0.2/hr. Compared to batch fermentation, maximum productivity was improved by as much as 13 times and cell mass production was increased by as much as 22 times. The diluted organic acids in the fermenter were selectively separated by liquid-liquid extraction using 30%(w/w) trioctylamine(TOA) dissolved in methylisobutylketone(MIBK). The degree of extraction was reached above 90% for both acetic and propionic acid through repeated extraction of organic acids in fermentation broth.

• Applied Biological Chemistry
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• v.40 no.1
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• pp.18-22
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• 1997

The conditions for production of high cell density of Bifidobacterium longum were investigated and the cross-flow filtration system was used to remove the inhibitory metabolites, lactic acid and acetic acid. The maximum cell growth was observed with glucose as carbon source at the concentration of 50 g/l at $37^{\circ}C$ with the initial pH 6.5. When B. longum was cultured in a cross-flow filtration system, the maximum cell growth was observed at a dilution rate(D) of $0.31\;h^{-1}$ and the dry cell weight was 16.4 g/l($3.5{\times}10^{10}\;cell/ml$), which was about four times higher than that obtained in the batch culture with pH control.