• KSBB Journal
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• v.18 no.5
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• pp.363-370
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• 2003

A filamentous fungus, strain FM04 producing amylase was isolated from rotten yam peels and potatoes. The favorable conditions of cultivation factors such as, temperature, pH, and agitation speed of strain FM04 were 28∼30$^{\circ}C$, 5.0∼6.0, and 100 rpm, respectively. Starch was the best carbon source in the amylase production. Therefore, food wastes containing lots of starch were employed as the carbon source of the cultivation for the economical amylase production. 5.2 U/ml of amylase was obtained In the cultivation using 1 % (w/v) of food wastes. The amylase showed the highest activity at enzyme reaction conditions of 60$^{\circ}C$ and pH 4.5 and showed 90% of residual activity after the reaction at 50$^{\circ}C$ for 2 days. In the enzymatic hydrolysis reaction using 20% (w/v) of food wastes and 2.5 U/ml of amylase, 72.6 g/l of reducing sugar was obtained at the reaction condition of 50$^{\circ}C$, pH 4.5 for 2 days.

• Applied Biological Chemistry
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• v.28 no.4
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• pp.233-238
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• 1985

Glucoamylases catalyze a stepwise hydrolysis of starch with the production of glucose. In order to make an efficient conversion of starch into glucose, glucoamylases prepared from Rhizopus spp. (Sigma Co.) were attached to a porous glass and immobilized by glutaraldehyde-induced crosslinking. The porous glass used in this study was $ZrO_2$ coated, $40{\sim}80$ mesh, 550 A pore diameter. Using the forgoing glass, we could couple as much as 50mg of protein per gram of carrier. Substrate for the glucoamylase was an enzyrne-modified thin-toiling 30% cornstarch solution used where greater solubility and low viscosity are desired. Immobilized glucoamylase had an optimum pH 7.0 to the alkaline side of soluble enzyme. Km values of immobilized and soluble enzyme were 1.04 mM and 1.25mM, respectively. The thermal stability of glucoamylase was increased by immobilization and the immobilized enzyme showed an optimum temperature at $40{\sim}60^{\circ}C$. The continuous conversion of cornstarch to glucose by use of immobilized glucoamylase resulted in the production of a more than 90 DE product.

• Food Science and Biotechnology
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• v.17 no.4
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• pp.755-760
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• 2008

The aim of this study was to produce resistant starch preparations from acid-modified com starches prepared at various hydrolysis levels (0.5-4.0 hr). Effect of autoclaving cycles on resistant starch (RS) formation was investigated. Molecular weight distribution, pasting and functional properties of acid-modified com starches were determined. For RS formation native and acid-modified starch samples were gelatinized and autoclaved (1 or 2 cycles). While native and acid-modified starches did not contain any RS, the levels increased to 9.0-13.5% as a result of storage at $95^{\circ}C$ after first autoclaving cycle. Second autoclaving cycle together with storage at $95^{\circ}C$ brought final RS contents of the samples incubated at 4 and $95^{\circ}C$ after the first cycle to comparable level. As acid modification level increased, the amount of high molecular weight fractions decreased, resulting in significant decreases in viscosities (p<0.05). The samples produced in this study had low emulsion stability and capacity values.

• Journal of Plant Biotechnology
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• v.36 no.3
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• pp.207-213
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• 2009

Starch serves not only as an energy source for plants, animals, and humans but also as an environmentally friendly alternative for fossil fuels. Progress in understanding of starch biosynthesis, and the isolation of many genes involved in this process have enabled the genetic modification of crops in a rational manner to produce novel starches with improved functionality. Starch is composed of two glucose polymers, amylose and amylopectin. The amylose and amylopectin ratio in starch affects its physical and physicochemical properties. Alteration in starch structure can be achieved by modifying genes encoding the enzymes responsible for starch biosynthesis and starch hydrolysis. Here, we describe recent findings concerning the starch modification in sweetpotato. Sweetpotato [Ipomoea batatas (L.) Lam] ranks seventh in annual production among food crops in the world as an important starch source. To develop transgenic sweetpotato plants with modifying starch composition, we constructed transformation vectors overexpressing granule bound starch synthase I and inhibiting amylopectin synthesis genes such as starch branching enzyme and isoamylase under the control of 35S promoter, respectively. Transformation of sweetpotato (cv. Yulmi) is in progress.

• Journal of Preventive Medicine and Public Health
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• v.7 no.1
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• pp.107-113
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• 1974

Many factors exert an influence on enzyme activity and thus on the rate of reactions that they catalyse. The most important of these factors are pH, temperature, substrate concentration, and the concentration of some inhibitors present. A solution of the enzyme diastase, which breaks down molecules of the polysaccharide starch to the disaccharide maltose by hydrolysis, was provided. Activity of this enzyme was measured by the rate at which starch was removed from the reaction mixture. These experiments were designed to study this reaction rate under varying conditions and the following results were obtained. 1. The range of optimum pH for this enzyme at room temperature was 4.0-7.0 and the optimum pH was 5.0. 2. The range of optimum temperatures for this enzyme at pH 7.0 was $30^{\circ}C-50^{\circ}C$ and the optimum temperature was $40^{\circ}C$. 3. The relationship between the enzyme activity and substrate concentration could be expressed by the Michaelis-Menten equation. The limiting velocity of this enzyme at room temperature and pH 7.0 was $415{\mu}g$ starch removed/ml of reaction mixture/min and $K_m$, Michaelis constant, was $343{\mu}g/ml$. 4. Inhibitors NaCl and $HgCl_2$ blocked this enzyme activity completely at 1% and 0.01% respectively.

• Mycobiology
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• v.39 no.4
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• pp.278-282
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• 2011

The objective of this study was to find useful fungi with ${\alpha}$-amylase activity from the Korean traditional nuruk for the quality of traditional Korean alcoholic beverage. In this study, 165 samples of traditional nuruk were collected from 170 regions throughout Korea and the fungi were isolated to a total of 384 strains. In order to investigate the effect of microflora on nuruk, ${\alpha}$-amylase activity, saccharogenic power (SP), starch hydrolysis activity and acid producing activity were evaluated. Ten strains were selected by ${\alpha}$-amylase activity, which ranged from 458.47 to 1,202.75 U/g. The size of the discolored zone for the starch hydrolysis activity of each fungus ranged from 0.3 to 2 cm. The SP of the 10 strains ranged from 228.8 to 433.4 SP. Of the 10 stains, three were identified as Aspergillus oryzae, two as Aspergillus flavus, two as Lichtheimia sp., one as Rhizopus oryzae and two as other strains. The total aflatoxins present in the nuruks were examined using enzyme-linked immunosorbent assay. The 10 nuruks had less than 1.11 ppb of aflatoxins.

• Proceedings of the Korean Biophysical Society Conference
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• 1999.06a
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• pp.35-35
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• 1999

Amylases catalyze the hydrolysis of starch material and play central roles in carbohydrate metabolism. The structure and a size exclusion column chromatography proved that the enzyme is a dimer in solution. The N -terminal segment of the enzyme folds into a distinct domain and comprises the enzyme active site together with the central (${\alpha}$/ ${\beta}$)$\sub$8/ barrel of the adjacent subunit.(omitted)

• Journal of Microbiology and Biotechnology
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• v.18 no.9
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• pp.1544-1549
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• 2008

MhMTS and MhMTH are trehalose ($\alpha$-D-glucopyranosyl-[1,1]-$\alpha$-D-glucopyranose) biosynthesis genes of the thermophilic microorganism Metallosphaera hakonensis, and encode a maltooligosyltrehalose synthase (MhMTS) and a maltooligosyltrehalose trehalohydrolase (MhMTH), respectively. In this study, the two genes were fused in-frame in a recombinant DNA, and expressed in Escherichia coli to produce a bifunctional fusion enzyme, MhMTSH. Similar to the two-step reactions with MhMTS and MhMTH, the fusion enzyme catalyzed the sequential reactions on maltopentaose, maltotriosyltrehalose formation, and following hydrolysis, producing trehalose and maltotriose. Optimum conditions for the fusion enzyme-catalyzed trehalose synthesis were around $70^{\circ}C$ and pH 5.0-6.0. The MhMTSH fusion enzyme exhibited a high degree of thermostability, retaining 80% of the activity when pre-incubated at $70^{\circ}C$ for 48 h. The stability was gradually abolished by incubating the fusion enzyme at above $80^{\circ}C$. The MhMTSH fusion enzyme was active on various sizes of maltooligosaccharides, extending its substrate specificity to soluble starch, the most abundant natural source of trehalose production.

• KSBB Journal
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• v.11 no.1
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• pp.86-91
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• 1996

Optimal reaction condition for the starch hydrolysis by ${\alpha}$-amylase was determined and the sugar produced under the optimal condition was measured for estimating the biodegradation of strach-filled polyethylene film. Optimal ranges of temperature and pH were 70~$80^{\circ}C$ and 6.3~7.3, respectively. The 100 units of ${\alpha}$-amylase per mg starch were enough for the enzyme reaction. Reaction with polyethylene film containing 5%, 10%, 15% and 20% starch in the above condition showed that the sugar produced was proportional to the starch content in film. This relationship provides a calibration curve for determining the starch content of search-filled polyethylene film. The average amount of hydrolyzed starch was about 40% of total starch in film. The rest of the starch is considered to be still dispersed in the film and not to be attacked by ${\alpha}$-amylase. In this experiment, we could obtain the higher biodegradability through the $\alpha$-amylase reaction in the above optimal condition than the reported one which had been Improved by adding surfactant.

• Korean Journal of Microbiology
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• v.13 no.3
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• pp.85-90
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• 1975

Crude cellulases freshly prepared from cultures of Aspergillus niger, Prnicillum motatum, Trichoderma vride 16273 and Trichoderma viride 16374 were assayed on 4 different substrates including Na-CMC, cellulose powder, starch and sucrose. Enzyme prepared from A. niger contained highly active hydrolytic enzymes of the 4 substrates assayed. P. notatum [yielded relatively lower amount of cellulase but the extracts were also highly reactive on starch and sucrose. Trichoderma viride 16274 yielded very little cellulase and invertase, but the extracts showed a high degree of amylase activity. Trichoderma viride 16374, however, yielded collulase comparable to that of Penicillium notatum, but lower activities of amylase and invertase were seen. Commercial cellulases prepared from Penicillium notatum (cellulase[K]) and Trichoderma viride(cellulase[J]) indicated enzyme activities closely parallel to the crude enzymes freshly prepared from fungus cultures. The optimum pH's of cellulolytic activities of cellulase[K] and cellulase[J] were 4.0 and 5.0 respectively. The optimum temperatures of the cellulolytic activities of cellulase[K] and cellualse[J] were 4.0 and 5.0 respectively. The optimum temperatures of the cellulolytic activities of cellulase [K] and cellulase [J] were $60{\circ}C$ and $50{\circ}C$ respectively. Assuming the average molecular weight of Na-CMC is about 115,000, the Km values of cellulase [K] and cellulase[J] were found to be $3.3{\times}10^{-5}/nM$ and $3.3{\times}10^{-4}/nM$ respectively.