• Korean Journal of Microbiology
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• v.15 no.1
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• pp.31-41
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• 1977

Dextrinogenic and glucoamylase activities of Aspergillus isolated from various habitat-substrates collected through South Korea are measured, and their amylase activities are surveyed in taxonomical and ecological viewpoints. 1. A. flavous group and A.wentii group exhibited higher activities for both amylases than others. 2. In the relations between amylase activity of Asperguillus and their habitat-sub-strates, the strains isolated from meju and cereals exhibited predominant dextrinogenic amylase activity. 3. Dextrinogenic amylase activity of Aspergillus is higher in the strains isolated from southern coast than the other regions. 4. Among the 601 strains of Aspergillus surveryed, strain No.74 and strain No.421 exhibited the most predominant activity for dextrinogenic amylase and glucoamylase, respectively.

• Journal of Microbiology and Biotechnology
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• v.20 no.4
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• pp.767-774
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• 2010

In this study, the problems of high caloric content, increased maturation time, and off-flavors in commercial beer manufacture arising from residual sugar, diacetyl, and acetaldehyde levels were addressed. A recombinant industrial brewing yeast strain (TQ1) was generated from T1 [Lipomyces starkeyi dextranase gene (LSD1) introduced, ${\alpha}$-acetohydroxyacid synthase gene (ILV2) disrupted] by introducing Saccharomyces cerevisiae glucoamylase (SGA1) and a strong promoter (PGK1), while disrupting the gene coding alcohol dehydrogenase (ADH2). The highest glucoamylase activity for TQ1 was 93.26 U/ml compared with host strain T1 (12.36 U/ml) and wild-type industrial yeast strain YSF5 (10.39 U/ml), respectively. European Brewery Convention (EBC) tube fermentation tests comparing the fermentation broths of TQ1 with T1 and YSF5 showed that the real extracts were reduced by 15.79% and 22.47%; the main residual maltotriose concentrations were reduced by 13.75% and 18.82%; the caloric contents were reduced by 27.18 and 35.39 calories per 12 oz. Owing to the disruption of the ADH2 gene in TQ1, the off-flavor acetaldehyde concentrations in the fermentation broth were 9.43% and 13.28%, respectively, lower than that of T1 and YSF5. No heterologous DNA sequences or drug resistance genes were introduced into TQ1. Hence, the gene manipulations in this work properly solved the addressed problems in commercial beer manufacture.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.6
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• pp.609-614
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• 2010

In the present study, bioethanol was produced using batch style reactor from food wastes which has organic characteristics. Pretreatment was required to reduce its particle size and produce fermentable sugar. Two different enzymes such as carbohydrase and gulcoamylase were tested for saccharification of food waste. The efficiency of carbohydrase saccharification (0.63 g/g-TS) has shown higher than glucoamylase saccharification(0.42 g/g-TS). Saccharomyces cerevisiae produced bioethanol via separate hydrolysis & fermentation (SHF) method and simultaneous saccharification fermentation (SSF) method. The production amount of bioethanol was 0.27 g/$L{\cdot}hr$ for SHF and 0.44 g/$L{\cdot}hr$ for SSF.

• 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.

• Journal of Microbiology and Biotechnology
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• v.25 no.1
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• pp.33-43
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• 2015

GAM-1 and GAM-2, two themostable glucoamylases from Aspergillus niger B-30, possess different molecular masses, glycosylation, and thermal stability. In the present study, the effects of additives on the thermal inactivation of GAM-1 and GAM-2 were investigated. The half-lives of GAM-1 and GAM-2 at 70℃ were 45 and 216 min, respectively. Data obtained from fluorescence spectroscopy, circular dichroism spectroscopy, UV absorption spectroscopy, and dynamic light scattering demonstrated that during the thermal inactivation progress, combined with the loss of the helical structure and a majority of the tertiary structure, tryptophan residues were partially exposed and further led to glucoamylases aggregating. The thermal stability of GAM-1 and GAM-2 was largely improved in the presence of sorbitol and trehalose. Results from spectroscopy and Native-PAGE confirmed that sorbitol and trehalose maintained the native state of glucoamylases and prevented their thermal aggregation. The loss of hydrophobic bonding and helical structure was responsible for the decrease of glucoamylase activity. Additionally, sorbitol and trehalose significantly increased the substrate affinity and catalytic efficiency of the two glucoamylases. Our results display an insight into the thermal inactivation of glucoamylases and provide an important base for industrial applications of the thermally stable glucoamylases.

• 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.

• Applied Biological Chemistry
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• v.43 no.1
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• pp.18-23
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• 2000

stract : Fourteen varieties of glutinous rices were examined on amylopectin fine structure and physicochemical properties of starch granules. The amylopectin chain length distribution and short chain/long chain ratio were investigated by enzymatic treatments followed by high-performance size-exclusion chromatographic separation. Chain length distribution profiles of the isoamylase-debranched amylopectins showed distinct patterns according to varieties. Beongok showed the highest short chain/long chain ratio, while TP2579A1 showed the lowest one. Sharebyeo-152-1-B showed the highest hydrolysis rate to 15% $H_2SO_4$, while Sandong 47 showed the lowest one. Fourteen varieties of rice starch granules showed A-type pattern on X-ray diffractograms. Non-gelitinized starch granules from Keochang 1 and Beongok had almost 100% hydrolysed by glucoamylase for 3 hrs at $370^{\circ}C$.

• Journal of Microbiology and Biotechnology
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• v.15 no.2
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• pp.239-246
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• 2005

Some characteristics of two forms of glucoamylase (glucan 1 A-$\alpha$-glucosidase, EC 3. 2. I. 3) purified from Aspergillus coreanus NR 15-1 were investigated. The enzymes were produced on a solid, uncooked wheat bran medium of A. coreanus NR 15-1 isolated from traditional Korean Nuruk. Two forms of glucoamylase, GA-I and GA-II, were purified to homogenity after 5.8-fold and 9.6-fold purification, respectively, judged by disc- and SDS-polyacrylamide gel electrophoresis. The molecular mass of GA-I and GA-II were estimated to be 62 kDa and 90 kDa by Sephadex G-1OO gel filtration, and 64 kDa and 91 kDa by SDS-polyacrylarnide gel electrophoresis, respectively. The optimum temperatures of GA-I and GA-II were 60$^circ$C and 65$^circ$C, respectively, and the optimum pH was 4.0. The activation energy (Ea value) of GA-I and GA-II was 11.66 kcal/mol and 12.09 kcal/mol, respectively, and the apparent Michaelis constants (K_{m}) of GA-I and GA-II for soluble starch were found to be 3.57 mg/ml and 6.25 mg/ml, respectively. Both enzymes were activated by 1 mM Mn^{2+} and Cu^{2+}, but were completely inhibited by 1 mM N­bromosuccinimide. The GA-II was weakly inhibited by 1 mM p-CMB, dithiothreitol, EDTA, and pyridoxal 5-phosphate, but GA-I was not inhibited by those compounds. Both enzymes had significant ability to digest raw wheat starch and raw rice starch, and hydrolysis rates of raw wheat starch by GA-I and GA-II were 7.8- and 7.3-fold higher than with soluble starch, respectively.

• Microbiology and Biotechnology Letters
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• v.14 no.4
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• pp.305-310
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• 1986

To improve the starch fermentation ability of yeast, hybrids were introduced by protoplast fusion of S. cerevisiae and S. diastaticus. The protoplasts of parental auxotrophic cells were fused in the presence of 10 mM CaCl$_2$and 30% of polyethyleneglycol (M.W 4, 000). The frequencies of fusant formation varied depending upon the strains used and were 3.51$\times$10$^{-4}$ to 5.04$\times$10$^{-4}$ for the regenerated protoplasts. The strains capable of extensive starch hydrolysis produce only 10% to total fusants. The 4 strains were finally selected by the results of starch fermentation and genetic stability test. The DNA content and cell volume of the fusants were greater than those of the parental strains.

• 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.