• Microbiology and Biotechnology Letters
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• v.29 no.1
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• pp.12-17
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• 2001

Aspergil-lus coreanus NR-15 and Aspergilus oryzae NR-2-5 from traditional Korean Nuruk were selected as parental strains producing starch hydrolysis enzyme. Xll(Arginine-) mutant from A. coreanus NR 15-1 showed high glu-doamylase activity and total acid productivity. Z6(Adenine-) mutant from A. oryzae NR2-5 showed the highest $\alpha$-amylase activity. Therefore, both XII and Z6 mutants were selected and investigated for the optimal conditions of protoplast formation for protoplast fusion. Mixture of equal amount of cellulase and driselase(10mg/ml each) was the most effective as lytic enzymes. The optimal pH and temperature for protoplast formation were 5.0 and $30^{\circ}C$, respectively. The most effective reaction for protoplast formation time was 4 hours. The maximum of protoplst for- mation of Xll mutant and Z6 mutant were $6.54$\times$10^{7}$ protoplasts/ ml and $3.04$\times$10^{ 7}$ protoplasts/ml, and the regen-eration frequencies of the protoplasts were 11.3% and 11.6%, respectively. The size of the protoplasts from X11 and Z6 mutants were 3~6 $\mu\textrm{m}$ and 4~9$\mu\textrm{m}$, respectively.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.6
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• pp.987-994
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• 2000

Aspergillus coreanus NR 15-1, Asp. oryzae NR 15-3 and Asp. oryzae NR 2-5 isolated from traditional Korean nuruk were screened as parental strains producing starch hydrolyzing enzymes. They were mutagenized by N-methyl -N'-nitro-N-nitrosoguanidine (NTG) and mutants were isolated for analysis of various amylase activities and the ability of acid production. Among them, the mutants harboring high saccharogenic activity, dextrinogenic activity, and the ability of acid production were selected. Fifteen, six, and five strains of mutants were isolated from Asp. coreanus NR 15-1, Asp. oryzae NR 2-5, and Asp. oryzae NR 15-3, respectively followed by NTG mutagenesis. Among these mutants, thirteen strains were identified as auxotrophic mutants. \ulcorner (Arg.￣) mutant from Asp. coreanus NR 15-1 showed high glucoamylase activity and total acid productivity. Z6 (Ade.￣) mutant from Asp. oryzae NR 2-5 showed the highest $\alpha$-amylase activity, therefore \ulcorner and Z6 mutant were selected.

• Journal of Microbiology
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• v.37 no.2
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• pp.80-85
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• 1999

The purification system of glucoamylase (glucan 1,4-${\alpha}$-glucosidase, EC 3. 2. 1. 3), some characteristics of the purified enzyme and hydrolysis rate of various raw starch were investigated through several experiments. The enzyme was produced on a solid, uncooked wheat bran medium of Aspergillus oryzae NR 3-6 isolated from traditional Korean Nuruk. The enzyme was homogeneously purified 6.8-fold with an overall yield of 28.3% by the criteria of disc- and SDS-polyacrylamide gel electrophoresis. The molecular weight was estimated to be 48 kDa by SDS-PAGE. The optimum temperature and pH were 55$^{\circ}C$ and 4.0, respectively. The enzyme was stable at a pH range of 3.0∼10.0 and below 45$^{\circ}C$. Enzyme activity was inhibited about 27% by 1mM Hg2+. The hydrolysis rate of raw wheat starch was shown to be 17.5-fold faster than the hydrolysis rate of soluble starch. The purified enzyme was identified as glucoamylase because the product of soluble starch by the purified enzyme was mainly glucose by thin layer chromatography.

• Microbiology and Biotechnology Letters
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• v.26 no.5
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• pp.456-464
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• 1998

For the standardization and quality improvement of traditional Korean Nuruk, 10 strains of fungi, which were isolated from Nuruks and showed good productivity of the saccharogenic and dextrinogenic enzymes, acid and flavor, were selected and their enzymological characteristics and identification were carried out. Aspergillus spp. and Rhizopus sp. showed a high liquefying activity without regard to cultivation time, whereas the majority of strains except for Rhizopus sp. had decreasing saccharifying activity in proportion to the increase in cultivation time. Aspergillus spp. No.17-2, No.17-6 and Rhizopus sp. No.18-1 showed high liquefying and saccharifying activity after 15 and 30 day cultivation. The optimum temperature of most of these saccharogenic and dextrinogenic enzymes was from 40$^{\circ}C$ to 60$^{\circ}C$, and their optimum pH was extensive between pH 3 and pH 11. But Penicillium spp.(2 strains) and Rhizopus sp. showed low activity under the alkalic and acidic conditions. Among these isolated strains, 5 strains which had shown the high productivity of materials were identified as Aspergillus oryzae NR3-6 and Aspergillus oryzae NR17-6, Aspergillus penicilloides NR12-1, Penicillium expansum NR7-7 and Rhizopus oryzee NRl8-1, respectively. Five kinds of mixed culture were carried out and all of them showed a better productivity of saccharogenic and dextrinogenic enzymes than single culture. These results indicate that it is possible to make traditional Korean liquors of good quality by using these fungi.

• Microbiology and Biotechnology Letters
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• v.10 no.3
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• pp.191-196
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• 1982

In order to prevent the losses of the rice by fungal deterioration during storage, fungal contaminants were isolated and identified from the grain samples (Milyang Nr.23) stored for seven months from December, 1978 to June, 1979 in silo, flat store and Tongari. Out of thirty cultures isolated from Korean paddy and brown rice samples, twenty seven species were identified, and there are eleven species of Aspergillus (A. caespitosus, A. condidus, A. chevalieri, A fischeri, A. fumigatus, A. flavus, A. nidulans, A. oryzae, A. ruber, A. sydowii, A. versicolor), five species of Penicillium (P. atramentosum, p. chrysogenum, P. cyaneofulvum, P. nototum, P. steckii), two species of each Alternaria (Al. faesiculata, Al. grisea) and Curvalaria (C, interseminata, C. tetromea), and one species of each Trichothecium roseum, Nigrospora sphaerica, Rhizopus nigricans, Fusarium spp., Mucor spp., Helminthosporium spp., and Gliocladiopsis spp. The major types of fungi grown on the surface of paddy during storage were A. flavus and A. candidus, while A. ruber and A. sydowii appeared in brown rice samples. And also A. candidus, A. versicolor and A. glacus groups were considered as major deteriorating microorganisms in stored brown and paddy rice in Korea.