• YAKHAK HOEJI
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• v.33 no.6
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• pp.365-371
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• 1989

Microbiological conversion of sterols to 17-ketosteroids has been recognized as a source for commercial preparation of steroidal drugs. In order to develop bacterial strains and process with Brevibacterium lipolyticum IAM 1398 capable of converting cholesterol to 1,4-Androstadiene-3,17-dione (ADD) at about 27% yield, we studied on strain improvement, fermentation condition and whole cell immobilization. By using UV and/or NTG as mutagens, a mutant to convert cholesterol to ADD with higher yield than 60% was selected. Better production of ADD was manifested in the case of maltose used as a supplemental carbon source, and yeast extract or soytone as a nitrogen source. Addition of tween 80 (0.05%) as a surfactant beneficial for increasing the productivity. The optimal initial pH of the medium was 6.5 and optimal culture temperature was $30^{\circ}C$. Whole cell immobilization by using carrageenan, agar, alginate and acrylamide was carried out and the activity of conversion was tested. In the case of carrageenan and agar, immobilized cells were active for at least two cycles of fermentation.

• Journal of Microbiology and Biotechnology
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• v.15 no.6
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• pp.1317-1322
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• 2005

This work describes neo-fructooligosaccharides (neo-FOSs) production using the immobilized mycelia of Penicillium citrinum. Some critical factors were evaluated to optimize maximal production of neo-FOS. Optimal alginate and cell concentrations were determined to be $1.96\%$ alginate and $7.17\%$ cell, respectively, by statistical analysis. The optimal concentration of $CaCl_{2}$, which is related to bead stability, was determined to be 2 M. It was possible to increase the neo-FOS production by adding 15 units of glucose oxidase to the batch reaction. By co-immobilizing cells and glucose oxidase, neoFOS productivity increased $123\%$ compared with the whole-cell immobilization process. Based on the results above, a co-immobilization technique was developed and it can be utilized for large-scale production.

• The Korean Journal of Mycology
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• v.11 no.3
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• pp.109-114
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• 1983

${\beta}-Galactosidase$ activity of Aspergillus phoenicis was studied using ONPG and lactose as substrate. It increased monotonically during the exponential growth phase and dropped rapidly at the beginning of the stationary one. It exhibited high tolerable temperature and acidic optimal pH which provides certain advantages from the industrial view point. Enzyme of ${\beta}-galactosidase$ had more subsrate affinity for ONPG than for lactose and its apparent maximum activity was also higher with the former as substrate. Activity of this enzyme depended upon the conditions of immobilization. Optimum crosslinking reaction was occurred at pH 7.2 and 0. 35 vol. % of glutaraldehyde concentration.

• Journal of Microbiology and Biotechnology
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• v.26 no.7
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• pp.1234-1241
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• 2016

Methanol is a versatile compound that can be biologically synthesized from methane (CH₄) by methanotrophs using a low energy-consuming and environment-friendly process. Methylocella tundrae is a type II methanotroph that can utilize CH₄ as a carbon and energy source. Methanol is produced in the first step of the metabolic pathway of methanotrophs and is further oxidized into formaldehyde. Several parameters must be optimized to achieve high methanol production. In this study, we optimized the production conditions and process parameters for methanol production. The optimum incubation time, substrate, pH, agitation rate, temperature, phosphate buffer and sodium formate concentration, and cell concentration were determined to be 24 h, 50% CH₄, pH 7, 150 rpm, 30℃, 100 mM and 50 mM, and 18 mg/ml, respectively. The optimization of these parameters significantly improved methanol production from 0.66 to 5.18 mM. The use of alginate-encapsulated cells resulted in enhanced methanol production stability and reusability of cells after five cycles of reuse under batch culture conditions.

• Journal of Microbiology and Biotechnology
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• v.18 no.11
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• pp.1803-1808
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• 2008

For practical application, the stability of permeabilized Ochrobactrum anthropi SY509 needs to be increased, as its half-life of enzymatic denitrification is only 90 days. As the cells become viable after permeabilization treatment, this can cause decreased activity in a long-term operation and induce breakage of the immobilization matrix. However, the organic solvent concentration causing zero cell viability was 50%, which is too high for industrial application. Thus, whole-cell immobilization using glutaraldehyde was performed, and 0.1% (v/v) glutaraldehyde was determined as the optimum concentration to maintain activity and increase the half-life. It was also found that 0.1% (v/v) glutaraldehyde reacted with 41.9% of the total amine residues on the surface of the cells during the treatment. As a result, the half-life of the permeabilized cells was increased from 90 to 210 days by glutaraldehyde treatment after permeabilization, and no cell viability was detected.

• Archives of Pharmacal Research
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• v.3 no.1
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• pp.7-12
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• 1980

Ampliciline was synthesized from 6-amino-pencillanic acid (6-APA) and D-.alpha. phenylglycine methyl ester by using amplicilin synthesizing enzyme from Peudomonas melanogenum (IAM 1655). The whole cell enzyme was immobilized by entrapping it in the polyacrylamide gel lattices. The polymer used in the enzyme entrapment was made from 150 mg per ml of acrylamide monomer and 8 mg per ml of N, N'-methylenebisacrylamide. About 200 mg/whole cell enzyme was mixed in the polymer for entrapment. The maximal activity retention after immobilization was 56%. The optimal pH values for the whole cell enzyme and the immobilized whole cell enzyme were 6.0 and 5.9, respectively. The optimal temperature for the enzyme activity were the same for both type of preparations. The enzyme stabilities against pH and heat increased for immobilized whole cell enzyme. Immobilized cell was more stable especially in the acidic condition while both type were found to be very suceptible to thermal inactivation at a temperature above 4.deg.C. The kinetic constants obtained from Lineweaver-Burk plot based on two substate reaction mechanism showed somewhat higher value for immobilized whole cell enzyme as compared to the whole cell enzyme : the Km value for 6-APA were 7.0 mM and 12.5 mM while Km values for phenylglycine methyl ester were 4.5 mM and 8.2 mM, respectively. Using the immobilized whole cell enzyme packed in a column reactor, the productivity of ampiciline was studied by varying the flow rate of substrate solution. At the space velocity, SV, 0.14 hr$^{-1}$ the conversion was 45%. Operational stability found in terms of half life was 30 hr at SV = 0.2 hr.

• Journal of Microbiology and Biotechnology
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• v.13 no.5
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• pp.687-691
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• 2003

Whole-cell immobilization of the hydrocarbon rich microalgae, Botryococcus braunii and B. protuberans, in alginate beads under air-lift batch cultures resulted in a significant increase in chlorophyll, carotenoid, dry weight, and 1ipid contents at stationary and resting growth phases, as compared to free cells. Photosynthetic activity in both the species, of Botryococcus was enhanced, relative to free cells, at any growth phase of cultures. Immobilization exerted a protective influence on ageing of the cultures as reflected by higher chlorophyll and dry weight contents. Entrapment also stabilized the chlorophyll and carotenoid contents even at stationary and resting phases as compared to free cells in both the species.

• The Korean Journal of Food And Nutrition
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• v.11 no.3
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• pp.319-322
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• 1998

The whole cell of alkalophilic Streptomyces sp. B-2 which produce glucose isomerase was immobilized by entrapment method for the effective production of high fructose syrup. The highest immobilized activity was achieved when the enzyme was bound to 2% $textsc{k}$-carrageenan. Immobilized glucose isomerase the pH optimum was about pH 7.5~8.5. Immobilization of alkalophilic Streptomyces sp. B-2 on 2% $textsc{k}$-carrageenan at 7$0^{\circ}C$ showed an increase in glucose isomerase activity. GI activity of immobilized cells was maximum Co2+ concentration 10-3M, Mg2+ concentration 10-3M.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 1978.10a
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• pp.207.2-207
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• 1978

Arthrobacter simplex (ATCC 6946) was cultured, induced and immobilized in acrylamide polymer. The characteristics of the immobilized whole-cell enayme were studied using hydrocortisone as the substrate. The enzyme activity was increased during the incubation of the gel particle in 0.5％ peptone media. The ennzyme reaction kinetics of the Δ'-dehydrogenase (3-oxosteroid Δ'-oxydo reductase, E. C. 1.3.99.4) foliowed the Michaelis-Menten type. Km and Vm values were different significantly after immobilization of the cell. The optimum pH and temperature were changed, too. Nitrogen sources such as casitone, peptone or tryptone were good media for the enzyme reaction. And there was no need to add cofactors of the enzyme in the pre-sence of energy sources used in the test. The effect of metal ions on the enzyme activity was insignificant. Organic solvents were used increase the substrate concentration and there was no optimum solvent concentration depending on the substrate concentration.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.468-472
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• 2003

Recently, genetic engineering techniques have been used to display various heterologous peptides and proteins (enzyme, antibody, antigen, receptor and fluorescence protein, etc.) on the yeast cell surface. Living cells displaying various enzymes on their surface could be used repeatedly as 'whole cell biocatalysts' like immobilized enzymes. We constructed a yeast based whole cell biocatalyst displaying T. reesei cellobiohydrolase I (CBH I ) on the cell surface and endowed the yeast-cells with the ability to degrade cellulose. By using a cell surface engineering system based on ${\alpha}-agglutinin,$ CBH I was displayed on the cell surface as a fusion protein containing the N-terminal leader peptide encoding a Gly-Ser linker and the $Xpress^{TM}$ epitope. Localization of the fusion protein on the cell surface was confirmed by confocal microscopy. In this study, we report on the genetic immobilization of T. reesei CBH I on the S. cerevisiae and hydrolytic activity of cell surface displayed CBH I.