• Mycobiology
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• v.44 no.3
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• pp.155-161
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• 2016

The most economically important species used in a wide range of fermentation industries throughout Asia belong to Aspergillus section Flavi, which are morphologically and phylogenetically indistinguishable, with a few being toxigenic and therefore a major concern. They are frequently isolated from Korean fermentation starters, such as nuruk and meju. The growing popularity of traditional Korean alcoholic beverages has led to a demand for their quality enhancement, therefore requiring selection of efficient non-toxigenic strains to assist effective fermentation. This study was performed to classify the most efficient strains of Aspergillus section Flavi isolated from various types of traditional wheat nuruk, based on a polyphasic approach involving molecular and biochemical evaluation. A total of 69 strains were isolated based on colony morphology and identified as Aspergillus oryzae/flavus based on internal transcribed spacer and calmodulin gene sequencing. Interestingly, none were toxigenic based on PCR amplification of intergenic regions of the aflatoxin cluster genes norB-cypA and the absence of aflatoxin in the culture supernatants by thin-layer chromatography analysis. Saccharification capability of the isolates, assessed through ${\alpha}-amylase$ and glucoamylase activities, revealed that two isolates, TNA24 and TNA15, showed the highest levels of activity. Although the degrees of variation in ${\alpha}-amylase$ and glucoamylase activities among the isolates were higher, there were only slight differences in acid protease activity among the isolates with two, TNA28 and TNA36, showing the highest activities. Furthermore, statistical analyses showed that ${\alpha}-amylase$ activity was positively correlated with glucoamylase activity (p < 0.001), and therefore screening for either was sufficient to predict the saccharifying capacity of the Aspergillus strain.

• Microbiology and Biotechnology Letters
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• v.42 no.4
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• pp.407-412
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• 2014

A number of Saccharomycopsis fibuligera strains that can hydrolyse and utilize starch as a carbon source were isolated from nuruk, a traditional Korean starter for rice wine fermentation, and their specific growth rates on starch-containing medium were compared to choose the prominent strain. S. fibuligera strain MBY1320 showed a higher growth rate at $42^{\circ}C$ than that of strain S. fibuligera KCTC7806, indicating that S. fibuligera MBY1320 has more thermo-tolerant machinery for starch hydrolysis and utilization than KCTC7806. Although the activity of ${\alpha}$-amylase at $30^{\circ}C$ was significantly lower for S. fibuligera MBY1320 than KCTC7806 (3,812.5 U vs. 14,878.5 U), S. fibuligera MBY1320 showed a much higher glucoamylase activity at $42^{\circ}C$ than S. fibuligera KCTC7806 (5,048.9 U vs. 13,152.3 U). Thus, a new S. fibuligera strain, with a higher starch-hydrolysing activity at elevated temperatures than that of other types of strain, this study reports.

• Korean Journal of Microbiology
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• v.32 no.4
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• pp.271-279
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• 1994

To develop a yeast strain which stably secretes both $\alpha$-amylase and glucoamylase and therefore is able to convert starch directly to ethanol, a mouse salivary $\alpha$-amylase cDNA gene with a yeast alcohol dehydrogenase I promoter has been introduced into the cell of a Saccharomyces diactaticus hybrid strain secreting only glucoamylase. To secrete both enzymes more stably without loss of the $\alpha$-amylase gene during a cell-multiplication, an integrating plasmid vector containing $\alpha$-amylase gene was constructed and introduced into the yeast cell. The results showed that the linearized form of the integrating vector was superior in the transformation efficiency and the rate of the expression of the $\alpha$-amylase gene than the circular type of the vector. The yeast transformant having a linearized plasmid vector exhibited higher mitotic stability than the yeast transformant habouring episomat plasmid vector. The transformant containing the linearized vector producing both $\alpha$-amylase and glucoamylase exhibited 2-3 times more amylolytic activity than the original untransformed strain secreting only glucoamylase.

• Journal of the East Asian Society of Dietary Life
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• v.25 no.1
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• pp.139-145
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• 2015

This study evaluated the functional characteristics of saccharified buckwheat (Fagopyrum esculentum) following ${\alpha}$-amylase, ${\beta}$-amylase or glucoamylase treatment based on changes in soluble solid contents, rutin and quercetin contents, total polyphenols and DPPH radical scavenging activity. The results showed that the amylase treatments significantly influenced the saccharification time. Additionally, total polyphenol, rutin, and quercetin contents increased during the saccharification process; increase in phenolic compounds induced antioxidant activity. The present study demonstrated that buckwheat has a higher amount of functional compounds and higher antioxidant activity after saccharification. These results show that buckwheat saccharification can be used to increase antioxidant capacity and functional value for applications in functional food industries.

• Korean journal of food and cookery science
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• v.19 no.1
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• pp.107-113
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• 2003

In a previous study, a dietary supplement was developed in our lab using natural herbal extracts against digest enzyme activity in GI tract for weight control. This natural herbal extracts could regulate absorption of glucose and lipid by the inhibition of digest enzyme activity. In this study, we screened the natural herbs that inhibit glucoamylase activity and developed an water extract of cinnamon. The cinnamon extract delayed and decreased the increment of carbohydrate degradation through the inhibition of glucoamylase activity in vitro. Fifty volunteers were subjected to the intake of the herbal extracts by taking twice a day for 60 days. As a result, the treated subjects lost 3 kg of body weight and 3.5 kg of body fat mass after the treatment. Furthermore, the body mass index and waist size were significantly decreased during the experimental period. Above results suggested that the administration of the dietary additives composed of cinnamon and natural herbal extract improves the obesity by the decrement of body weight and body fat mass.

• Microbiology and Biotechnology Letters
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• v.18 no.3
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• pp.251-259
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• 1990

Asp. usumii IAM 2185 was selected as a strain producing the powerful raw starch digesting glucoamylase. The optimum initial pH, the optimum temperature and the optimum cultural time for the enzyme production on wheat bran medium were pH 6-8,25-$30^{\circ}C$ and 72 hrs, respectively. The addition of ammonium nitrate and albumin on wheat bran medium, respectively, increase slightly the enzyme production. The enzyme was purified by ammonium sulfate fractionation, CM-cellulose and DEAE-cellulose column chromatography. The specific activity of the purified enzyme was 34.3 U/mg protein and the yield of enzyme activity was 10.3%. The purified enzyme showed a single band on polyacrylamide disc gel electrophoresis and its molecular weight was estimated to be 67,000 by SDS polyacrylamide disc gel electrophoresis. The isoelectric point for the purified enzyme was pR 3.7. The optimum temperature and optimum pH were $60^{\circ}C$and pH 3.0 and the purified enzyme was stable in the pH range of 1.0-11.0. The purified enzyme was stable below $50^{\circ}C$ and its thermostability was greatly increased by the addition of $Ca^{2+}$. The purified enzyme showed a high hydrolysis rate on various raw starches such as corn, rice, yam, arrow root, sweet potato and glutinous rice.

• Journal of the East Asian Society of Dietary Life
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• v.1 no.1
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• pp.99-111
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• 1991

In each nuruk using today, effect of pH on glucoamylase activity and viable cell count of yeast and bacteria was measured. Common components during fermentation, alcohol, acetaldehyde and acetone, amino acid composition, and total sugars and mineral content were determined in yakju(korean wine) brewed from different ingredients and by different methods. Results are summarized as follows ; 1. The lower the pH, the lower the glucoamylase activity in JK, BK, JK-S BK-S and JN. But the higher the glucoamylase activity ratio in Koji and KN. 2. Yeast and bacteria cell count could not determined in nuruk inoculated of seed. In JK, BK and JN, yeast cell count was 50${\times}$104∼80${\times}$104, bacteria cell count was 5${\times}$106∼24${\times}$106. 3. In yakju during fermentation, pH was higher in RU, total acidity content was higher in ST-N, ST-K, RU and ST-RUPO and alcohol content was lower in RUPO and ST-RUPO. 4. Ethanol and acetaldehyde content were highest in dukyunju. Trace amount of acetone was determined only in ST-K, RUPO and ST-RUPO . n-Propyl alcohol content was higher in ST-K, ST-RUPO and ST-N, iso-butyl alcohol content was higher in L-RUPO, Dukyunju and Songyupju and iso-amyl alcohol content was higher in Songyupju, RU, L-RUPO and Dukyunju. 5. In amino acids composition of each yakju, Pro, Ala and Val content was higher than other amino acids. Total amino acids content was the highest in Dukyunju and second highest in ST-N, NH3 was higher in ST-N, Dukyunju, RUPO than other samples. 6. Total sugars content was the highest in ST-N and second highest in RU. 7. P, K and Mg content were higher in Dukyunju and ST-N than in other samples. In Dukyunju, Ca and P ratio was 0.075 because of low Ca content and high P content.

• KSBB Journal
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• v.23 no.4
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• pp.345-349
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• 2008

To enhance the value as a feedstuff of distiller's dried grain (DDG) and develop fermented feedstuff, we investigated the effects of the culture conditions affecting glucoamylase activity, such as pH in submerged culture and moisture content in solid-state culture. Also, we investigated the optimal mixing ratio of DDG and wheat bran for the production of fermented feedstuff containing high content of amino acids. In culture conditions for high fermented activity, pH and moisture were optimum at pH 4 and 60%, respectively. In the case of mixing ratio, the glucoamylase activity was decreased with increase of DDG content. On the other hand, the content of crude protein was increased slowly. For the development of fermented feedstuff, the optimal mixing ratio of DDG and wheat bran was 1 to 4. Finally, we could produce approximately 1 ton (dry matter) of trial product in incubator of pilot-scale. The glucoamylase activity and the crude protein content were 1,024 U/g and 33.6%, respectively.

• Korean Journal of Food Science and Technology
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• v.13 no.3
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• pp.241-246
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• 1981

A fungal strain which produced high levels of acid protease and amylase was isolated from the atmosphere for application to the manufacture of digestive enzme preparation. This study was carried out to elucidate its microbiological characteristics, environmental conditions for production of the enzymes, and relationships between the enzyme activity and acidity. 1. The isolate was identified as a fungal strain which belonged to Aspergillus niger by the manual of Rafer and Fennel, and was found to be a strain producing high levels of acid protease and amylase. 2. The optimal pH of tile enzymes produced by the strain were: protease, 2.0;, ${\alpha}-amylase$, 4 to 5; and glucoamylase, 3 to 5. 3. The optimal culture conditions for production of the enzymes were: protease (at pH 2.5), 2 to 3 days incubation on wheat bran at $30^{\circ}C$; ${\alpha}-amylase$ and glucoamylase(at pH 3.0), 3 days incubation at $30^{\circ}C$. 4. The production of acid protease and glucoamylase was increased approximately by 20 percent when 2 percent of corn starch was added to the wheat bran medium. 5. The addition of 0.3 percent ammonium sulfate to the wheat bran medium resulted in enhancing the enzyme production, especially of acid prctease.

• Microbiology and Biotechnology Letters
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• v.13 no.3
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• pp.223-232
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• 1985

To find microorganisms of producing $\alpha$-amylase inhibitors, actinomycetes were isolated from soil samples that were collected at different locations in Korea and screened for enzyme inhibitory activity. A strain of these microbes had a high inhibitory activity and was identified as one of the genus Streptomyces by morphological, biochemical and physiological studies according to the methods of the International Streptomyces Project (ISP). The medium used consisted of 3 ％ corn starch, 0.2％ yeast extract and 0.8％ peptone (pH 7.0). When this strain was aerobically cultured in the medium on a rotary shaker, the highest inhibitory activity was obtained after four days. This inhibitor had inhibitory activities on various $\alpha$-amylases and glucoamylase, but not on $\beta$-amylase.