• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.779-781
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• 2001

Human leptin is a 16kDa protein and is known to influence body weight control. It is composed of 146 amino acids. In this study, human leptin gene was obtained from homosapiens leptin mRNA using RT-PCR. And leptin gene was inserted into secretion vectors and Saccharomyces cerevisiae was transformed. In flask culture, Saccharomyces cerevisiae transformant showing high leptin expression titre was selected and with the best transformant, fed-batch fermentation and purification was optimized. As a result, about 2 g/L of leptin was expressed and the yield of purification was about 80%.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.145-148
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• 2003

High concentration of glutathione(GSH) has been found in some species of yeast, of which Saccharomyces cerevisiae is used for commercial fermentative production. In this study, we have investigated the optimal conditions of production which could increase the GSH productivity and used it to maximize the production of GSH in fed-batch culture of Sacchromyces cerevisiae. Fermentation process have been also real time monitored by a 2-dimensional fluorescence sensor.

• KSBB Journal
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• v.14 no.5
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• pp.561-565
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• 1999

Optimum conditions for vacuum-drying ad cultivation of yeast cells for the production of active dry yeast were examined. At lower temperature, more drying time was required to dry the yeast pellet to reach the desirable water content(8%). Optimum temperature of vaccum oven and time for drying was 63$^{\circ}C$ and 90 min, respectively. Optimum medium composition for flask culture using cane molasses as the substrate were 0.25% sugar, 0.013% $K_2$HPO$_4$, 0.1% $K_2$HPO$_4$. and 0.125% (NH$_4$)$_2$SO$_4$. Culture temperature $25^{\circ}C$ gave the highest survival rate of dired yeast. After finishing fed-batch culture and the culture was left in the fermentor without adding any sugar or nutrient, survival of the dried yeast harvested from the fermentor increased to 86.0% after 36 hr. It was also observed that the yeast cells with higher budding rates showed lower survival rate.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.676-679
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• 2003

Long time over 6 month was required to form granuler sludge, which is critically necessary for UASB reactor. By feeding both high molecular cationic polymer and anionic silica sol to conventional digestion sludge, granular sludge was obtained within 5 minutes. Succession adaptation was performed for granular sludge for 30 days. $80{\sim}90%$ COD removal efficiency was shown with granular sludge, which was comparable with that of typical UASB granular sludge.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.153-156
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• 2003

The MRS medium is widely used as an optimized medium for the growth of Lactobacillus spp. and also used for the growth of Leuconostoc spp. Leuconostoc mesenteroides shows quite different physicochemical properties compared to Lactobacilli spp. and it is one of the major strain of kimchi fermenting microorganisms with its usefulness in our traditional foods and availability in biotechnology in the future, specifically tailor-made medium is necessary for the growth of Leuconostoc mesenteroides. Sequential experimental designs (Plackett-Burman, fractional factorial, steepest ascent, central composite design and response surface methodology) were introduced to optimize and improve the Leuconostoc medium. Fifteen medium ingredients were investigated and fructose, sodium acetate and ammonium citrate were determined to give a critical and positive effect for cell-growth. The yield of biomass using the optimal medium was improved more than that of the MRS medium and the result of fed-batch culture showed the capability of the improvement in cell mass similar to the E.coli system.

• Journal of Microbiology and Biotechnology
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• v.10 no.4
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• pp.564-567
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• 2000

A recombinant Saccharomyces cerevisiae, transformed with the genes encoding xylose reductase (XYL1) and xylitol dehydrogenase (XYL2) orginated from Pichia stipitis CBS 5776, was developed to directly convert xylose to ethanol. A fed-batch fermentation with the recombinant yeast produced 8.7 g ethanol/l with a yield of 0.13 g ethanol/g xylose consumed.

• Journal of Microbiology and Biotechnology
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• v.25 no.6
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• pp.845-855
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• 2015

The present study describes the gene cloning and high-level expression of an alkaline and thermostable lipase gene from Trichosporon coremiiforme V3. Nucleotide analysis revealed that this lipase gene has an open reading frame of 1,692 bp without any introns, encoding a protein of 563 amino acid residues. The lipase gene without its signal sequence was cloned into plasmid pPICZαA and overexpressed in Pichia pastoris X33. The maximum lipase activity of recombinant lipase was 5,000 U/ml, which was obtained in fed-batch cultivation after 168 h induction with methanol in a 50 L bioreactor. The purified lipase showed high temperature tolerance, and being stable at 60℃ and kept 45% enzyme activity after 1 h incubation at 70℃. The stability, effects of metal ions and other reagents were also determined. The chain length specificity of the recombinant lipase showed high activity toward triolein (C18:1) and tripalmitin (C16:0).

• Microbiology and Biotechnology Letters
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• v.23 no.2
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• pp.220-228
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• 1995

For polyhydroxyalkanoic acid (PHA) production, several microorganisms were isolated from sewage sludge. One of them, GB-77 strain, was chosen from its PHB/HV copolymer production on only fructose without cosubstrate. The isolated strain GB-77 was identified as the genus Alcaligenes. Optimal temperature and pH for cell growth were 36C and 6.8. Optimal medium composition was 10 g/l of fructose and 5 g/l of polypeptone, 1 $\times$ 10$^{-2}$M Na$^{2}$HP0$^{4}$, 1.3 $\times$ 10$^{-2}$M KH$^{2}$PO$^{4}$. To investigate the optimal condition for polyhydroxyalkanoic acid production two-stage culture technique was used; first stage for cell growth and second stage for PHA production on unbalanced growth conditions. Optimal conditions for high PHA production were C/N ratio 50, temperature 36$\circ$C and pH 6.8. To overcome fructose inhibition on cell growth, intermittent feeding fed-batch culture technique was used. Total cell concentration was 17.4 g/l with 9.1 g/l of PHA. The purified PHA was identified PHB/HV copolymer by NMR analysis.

• Microbiology and Biotechnology Letters
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• v.19 no.1
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• pp.70-75
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• 1991

Continuous and simultaneous production of gluconic acid and sorbitol from glucose and fructose was carried out by using glucose-fructose oxidoreductase and glucanolactonase of Zymomonas mobilis. In order to utilize the enzymes without purification, Zymomonas mobilis was permeabilized with toluene. Optimum conditions for permeabilization and reaction kinetics of permeabilized Zymomonas mobilis were studied. In batch operation with the permeabilized cells immobilized in alginate beads, about 90% conversion was obtained within 35 h reaction. Continuous production of gluconic acid and sorbitol using the immobilized permeabilized cells was carried out. Optimum conditions for continuous operation with the imn~obilized cells were; pH 6.2 and temperature $40^{\circ}C$. Maximum productivities for gluconic acid and sorbitol were about 14.5 g/l/h and 14.8 g/l/h respectively at the dilution rate of 0.075 $h^{-1}$ when 300 g/l each of substrates was fed.

• Journal of Microbiology and Biotechnology
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• v.24 no.12
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• pp.1685-1689
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• 2014

Baeyer-Villiger (BV) oxidation of cyclohexanone to ${\varepsilon}$-caprolactone in a microbial system expressing cyclohexanone monooxygenase (CHMO) can be influenced by not only the efficient regeneration of NADPH but also a sufficient supply of oxygen. In this study, the bacterial hemoglobin gene from Vitreoscilla stercoraria (vhb) was introduced into the recombinant Escherichia coli expressing CHMO to investigate the effects of an oxygen-carrying protein on microbial BV oxidation of cyclohexanone. Coexpression of Vhb allowed the recombinant E. coli strain to produce a maximum ${\varepsilon}$-caprolactone concentration of 15.7 g/l in a fed-batch BV oxidation of cyclohexanone, which corresponded to a 43% improvement compared with the control strain expressing CHMO only under the same conditions.