• Journal of Microbiology and Biotechnology
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• v.22 no.11
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• pp.1486-1493
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• 2012

In this study, we investigated whether galactooligosaccharide (GOS) can be stably and steadily synthesized using immobilized ${\beta}$-galactosidase (${\beta}$-gal) inclusion body (IB)-containing E. coli cells during long-term repeated-batch operation. To improve the operational stability of this enzyme reactor system, immobilized E. coli cells were crosslinked with glutaraldehyde (GA) after immobilization of the E. coli. When we treated with 2% GA for E. coli crosslinking, GOS production continued to an elapsed time of 576 h, in which seven batch runs were operated consecutively. GOS production ranged from 51.6 to 78.5 g/l ($71.2{\pm}10.5$ g/l, n = 7) during those batch operations. In contrast, when we crosslinked E. coli with 4% GA, GOS production ranged from 31.5 to 64.0 g/l ($52.3{\pm}10.8$, n = 4), and only four consecutive batch runs were operated. Although we did not use an industrial ${\beta}$-gal for GOS production, in which a thermophile is used routinely, this represents the longest operation time for GOS production using E. coli ${\beta}$-gal. Improved stability and durability of the cell immobilization system were achieved using the crosslinking protocol. This strategy could be directly applied to other microbial enzyme reactor systems using cell immobilization to extend the operation time and/or improve the reactor system stability.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1277-1283
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• 1990

The iterative learning control synthesized in the frequency domain has been utilized for temperature control of a batch reactor. For this purpose, a feedback-assisted generalized learning control scheme was constructed first, and the convergence and robustness analyses were conducted in the frequency domain. The feedback-assisted learning operation was then implemented in a bench scale batch reactor where reaction heat is simulated using an electric heater. As a result, progressive reduction of temperature control error could be obviously observed as batch operation is repeated.

• Mycobiology
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• v.40 no.1
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• pp.35-41
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• 2012

A repeated batch fermentation system was used to produce ethanol using $Saccharomyces$ $cerevisiae$ strain (NCIM 3640) immobilized on sugarcane ($Saccharum$ $officinarum$ L.) pieces. For comparison free cells were also used to produce ethanol by repeated batch fermentation. Scanning electron microscopy evidently showed that cell immobilization resulted in firm adsorption of the yeast cells within subsurface cavities, capillary flow through the vessels of the vascular bundle structure, and attachment of the yeast to the surface of the sugarcane pieces. Repeated batch fermentations using sugarcane supported biocatalyst were successfully carried out for at least ten times without any significant loss in ethanol production from sugarcane juice and molasses. The number of cells attached to the support increased during the fermentation process, and fewer yeast cells leaked into fermentation broth. Ethanol concentrations (about 72.65-76.28 g/L in an average value) and ethanol productivities (about 2.27-2.36 g/L/hr in an average value) were high and stable, and residual sugar concentrations were low in all fermentations (0.9-3.25 g/L) with conversions ranging from 98.03-99.43%, showing efficiency 91.57-95.43 and operational stability of biocatalyst for ethanol fermentation. The results of the work pertaining to the use of sugarcane as immobilized yeast support could be promising for industrial fermentations.

• Journal of Microbiology and Biotechnology
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• v.25 no.3
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• pp.366-374
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• 2015

Herein, we established a repeated-batch process for ethanol production from glycerol by immobilized Pachysolen tannophilus. The aim of this study was to develop a more practical and applicable ethanol production process for biofuel. In particular, using industrial-grade medium ingredients, the microaeration rate was optimized for maximization of the ethanol production, and the relevant metabolic parameters were then analyzed. The microaeration rate of 0.11 vvm, which is far lower than those occurring in a shaking flask culture, was found to be the optimal value for ethanol production from glycerol. In addition, it was found that, among those tested, Celite was a more appropriate carrier for the immobilization of P. tannophilus to induce production of ethanol from glycerol. Finally, through a repeated-batch culture, the ethanol yield (Y_e/g) of 0.126 ± 0.017 g-ethanol/g-glycerol (n = 4) was obtained, and this value was remarkably comparable with a previous report. In the future, it is expected that the results of this study will be applied for the development of a more practical and profitable long-term ethanol production process, thanks to the industrial-grade medium preparation, simple immobilization method, and easy repeated-batch operation.

• KSBB Journal
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• v.25 no.2
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• pp.187-192
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• 2010

We designed the optimal operational strategy in repeated fed-batch ethanol fermentation using Sacchromyces cerevisiae ATCC 24858 in views of ethanol yield, specific ethanol production rate, and ethanol productivity, when the aeration rate were controlled at 0.0 and 0.33 vvm. Coincidentally, the time intervals of withdrawal-fill of culture medium (24 and 36 h) were investigated. Ethanol yield and ethanol productivity when the aeration was carried out at 0.33 vvm were superior to those when the aeration was not carried out. Additionally, those parameters when the time interval of withdrawal-fill of culture medium was 24 h were superior to those when time interval of withdrawal-fill of culture medium was 36 h. The total ethanol production reached at the greatest value, 703.8 g-ethanol, when the aeration was carried out at 0.33 vvm and the time interval of withdrawal-fill of culture medium was 24 h. In this study, we verified experimentally the necessity of designing the operational strategy for increasing ethanol production in terms of aeration rate and time interval of withdrawal-fill of culture medium in the repeated fed-batch ethanol fermentation.

• Korean Journal of Food Science and Technology
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• v.29 no.2
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• pp.343-347
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• 1997

Effect of culture conditions on the fermentation of wheat flour solution by mixed lactic acid bacteria of Lactobacillus brevis, L. fermentum and L. plantarum was investigated. The optimum temperature for the fermentation of wheat flour solution was $35^{\circ}C$ because pH decreased the lowest value and TTA (total titrable acidity) increased the highest value at this temperature. In aerobic condition, fermentor was purged with air at 1.0 vvm and was purged with nitrogen gas at 1.0 vvm in anaerobic condition. The decrease of pH and the increase of TTA in aerobic condition were higher than those in anaerobic condition. In aerobic condition, the optimum condition of oxygen supply was found to be oxygen transfer rate coefficient of $60\;hr^{-1}$ which corresponded to agitation speed of 250 rpm in a 5 L fermentor. Repeated fed-batch cultures were performed using pH-stat in order to increase the productivity of fermented wheat flour. With increasing the repeated fraction of culture volume, mean cycle time increased but maximum operation time decreased. However, the volume of produced broth per culture volume per time and total volume of produced broth per culture volume were maximum at the repeated fraction of culture volume of 20%. In a repeated fed-batch fermentation of wheat flour solution using mixed lactic acid bacteria, the culture condition was optimum at temerature of $35^{\circ}C$, aeration rate of 1.0 vvm, oxygen transfer rate coefficient of $60\;hr^{-1}$, and repeated fraction of culture volume of 20%.

• KSBB Journal
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• v.10 no.1
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• pp.55-62
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• 1995

The functional relationship between the initial cell concentration and the ethanol productivity was investigated in the repeated batch fermentation of Sacharomyces cerevisiae ATCC 24858. The repeated batch fermentations were performed in the range of 60 to $150g/\ell$ of initial sugar concentration and 17.5g/$\ell$ to $53.1g/\ell$ of initial cell concentration. The time of one batch fermentation was 1 or 2 hours and the batch fermentation was repeated ten times in every repeated formentaction. The functional relationship showed that the productivity increased non-linearly according to the increase of initial cell concentration regardless of initial sugar concentration. When the initial concentration of sugar was $60g/\ell$ and that of biomass was $34.5g/\ell$, the fermentation was completed within one hour and its ethanol productivity was $26.7g/\ell$.hr, the latter including the times of cell separation, pouring the new substrate into a flask and sampling. When the initial sugar concentration was $120g/\ell$ and the initial cell concentration $50.3g/\ell$, the fermentation was also finished within one hour and its productivity was $45.8g/\ell$$.$hr, The maximum ethanol productivity for eight different repealed fermentations in this work was $53g/\ell$.hr.

• KSBB Journal
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• v.7 no.4
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• pp.284-289
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• 1992

The optimum conditions for the production of tryptophan using a recombinant Klebsiella pnuemoniae phe A tyr A trp R/pSC 101-$trp^{+}$ and its plasmid stability during tryptophan production were studied. The optimum temperature was $37^{\circ}C$ and the specific growth rate was 1.05$h^{-1}$ at $37^{\circ}C$. Tryptophan production was increased by glucose fed-batch culture, and tryptophan was accumulated to 0.175 g/l after 36 hrs. This amount was about 1.2 and 1.6 times greater than that obtained from batch culture and flask culture, respectively. The stability of the strain in fed-batch cu1ture was greatly different from that in repeated flask culture. After 6 generation, 95% of total cells was stable in repeated flash culture, but in fed-batch culture only 50% was stable.

• KSBB Journal
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• v.17 no.1
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• pp.14-19
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• 2002

The objective of this study is to investigate optimum condition for lignin peroxidase production by white rot fungi Phanerochaete chysosporium IFO 31249 immobilized in a rotating bioreactor. The maximum lignin peroxidase activity of batch culture in rotating bioreactor was 300 U/L. The optimum rotating speed and packing ratio of support for lignin peroxidase production in a rotating bioreactor were 1 rpm and 20%, respectively. The optimum concentration of $MnSO_4$$\cdot$$H_2O$ for manganese-dependent peroxidase production in a rotating bioreactor was 50 ppm. The sufficient supply of oxygen was the most important factor to achieve maximum lignin peroxidase production. It was possible to produce lignin peroxidase (LiP) and manganese-dependent peroxidase (MnP) for at least 3 times successive repeated-batch cultures, respectively.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.410-413
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• 2001

In this study a repeated batch production of lactic acid was investigated for the purpose of reducing amount of yeast extract dosage. First batch operation was performed with nutrient rich media(glucose 100-150 g/${\ell}$, and high yeast extract contents; 15 g/${\ell}$), and subsequential batch operations were performed with nutrient poor media(glucose 100-150 g/${\ell}$, and reduced yeast extract contents; 4-5 g/${\ell}$). Volumetric productivities(6.03-6.20 g/${\ell}{\cdot}h$) and substrate conversion rate(94-98%) of eve η subsequential batch operation were maintained with the same level of first batch operation(6.19 g/${\ell}{\cdot}h$, and 99%, respectively), when concentrations of glucose and yeast extract were 100, and 4 g/${\ell}$ respectively.