• Microbiology and Biotechnology Letters
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• v.44 no.3
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• pp.376-382
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• 2016

The amylolytic enzyme activities of nuruks collected or produced in this study were examined. A maximum α-amylase activity of 24,747.1 ± 777.7 units/mg protein was obtained for a nuruk incubated at a relative humidity of 40% at 30℃. A nuruk matured at a relative humidity of 50% at 25℃ showed the highest glucoamylase acitivity. Among the 98 fungal strains isolated from the nuruk exhibiting the highest amylolytic enzyme activities, 26 strains of Aspergillus oryzae and 18 strains of Rhizopus oryzae were identified. Rhizopus oryzae MBF345 showed an α-amylase activity of 36,724.9 ± 10.2 units/mg protein and a glucoamylase activity of 4,911.8 ± 48.1 SP. These values were 1.7-fold and 1.4-fold greater, respectively, than those of the control strain. Strain MBF345 was deposited as KCTC46312 in the Korean Culture Type Collection.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.7
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• pp.1002-1008
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• 2012

For the production of Korea traditional cereal wine makgeolli, a rice fermentation starter nuruk was Rhizopus oryaze CCS01 commercial nuruk. The carbohydrate content of rice nuruk was higher, the levels of moisture, ash, crude protein, and crude fat were lower. In particular, the saccharifying activity of rice nuruk was 2.2 times higher than commercial nuruk. pH, alcohol, and viable yeast cells of makgeolli made rice nuruk were higher than those of makgeolli made commercial nuruk. In contrast, the levels of acidity, $^{\circ}Brix$, viable lactic acid bacteria (LAB) cells, and browning of makgeolli made rice nuruk were lower than those of makgeolli made commercial nuruk, the alcohol content of glutinous rice (GUR) makgeolli made rice nuruk higher other samples. These results suggest that rice nuruk R. oryzae CCS01 make new type cereal makgeolli.

• Journal of the East Asian Society of Dietary Life
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• v.27 no.3
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• pp.348-363
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• 2017

We analyzed the mixed culture characteristics of isolated brewing fungi obtained from Korean traditional nuruk for their development as fermentation starters. In a previous study, we selected appropriate fungi strains based on their large fungi bodies and strong enzyme activities. These fungi strains were mixed cultured under various combination of ratios, pHs and temperatures. As a result, total acidities of R. delemar mixed culture media were higher than those of A. oryzae cultured at $20^{\circ}C$ and $37^{\circ}C$. The pHs of A. luchuensis 34-1 and A. oryzae 37-7 as well as R. delemar 58-8 and A. oryzae 37-7 mixed culture media gradually increased with the culture period. On the contrary, total acidities of the mixed culture media gradually decreased. ${\alpha}-Amylase$ activities of R. delemar 26-4 and R. oryzae 82-7 mixed culture media were strong at $20^{\circ}C$ and pH 4, glucoamylase activities of R. delemar 58-8 and A. oryzae 37-7 were strong at $37^{\circ}C$, pH 3 and 1:2 ratio, and acidic protease activities of R. delemar 26-4 and A. oryzae 78-5 were strong at $20^{\circ}C$, pH 4 and 1:4 ratio. This study provides the optimal mixed culture conditions for fermentation starters based on changes in pH and total acidity, favorable enzyme activities, and fungi varieties.

• Microbiology and Biotechnology Letters
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• v.43 no.2
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• pp.169-174
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• 2015

Nuruk has been used as fermentation starter in the alcohol industry for some time in Korea. Various bioactivities, such as antiproliferative and anti-obesity, of R4 nuruk made from Rhizopus oryzae KSD-815 have been previously reported. In this study, the hot water and ethanol extract of R4 nuruk and their subsequent organic solvent fractions were prepared, and their antithrombosis activities were evaluated. The ethylacetate fraction showed strong anti-coagulation activity, and the ethylacetate and butanol fraction from hot water extract demonstrated platelet aggregation inhibitory activity, without hemolysis against human RBC. Our results suggest that R4 nuruk has the potential to act as a new anti-thrombosis agent.

• The Korean Journal of Mycology
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• v.42 no.3
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• pp.191-200
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• 2014

Nuruk samples collected from various regions in Korea were investigated in terms of fungal contents and diversity. In measurement of colony forming unit (CFU) in Nuruk suspensions on DRBC agar, Nuruk samples MS4, MS8, and MS10 were among the highest fungal density, with $1,278.9{\pm}21.6$ (${\times}10^4$), $1,868.0{\pm}27.7$ (${\times}10^4$), and $775.1{\pm}19.2$ (${\times}10^4$) were among the samples showing the highest fungal density. CFU per 20 mg Nuruk, respectively. The majority of fungal components were yeasts, including Pichia anomala, P. kudriavzevii, Kluyveromyces marxianus, and Saccharomycopsis fibuligera, whereas Aspergillus oryzae and Rhizopus oryzae, the representative Nuruk fungi, were predominant only in the low fungal density Nuruks (MS2, MS5, and MS11). Saccharification capability of the fungal isolates was assessed by measurement of amylase activity in the culture broth. The highest amylase activity was found in A. niger and A. luchuensis, followed by S. fibuligera. A. oryzae and R. oryzae showed fair amylase activity but significantly lower than those of the three fungal species. R. oryzae was suggested to play an additional role in degradation of ${\beta}$-glucan in crop component of Nuruk since R. oryzae was the only fungus that showed ${\beta}$-glucanase activity among the fungal isolates. To confirm the safety of Nuruk, aflatoxigenicity of the isolated Aspergillus was estimated using the DNA markers norB-cypA, aflR, and omtA. All of the isolates turned out to be non-aflatoxigenic as evidenced by the deletion of gene markers, norB-cypA and aflR, and the absence of aflatoxin in the culture supernatants shown by TLC analysis.

• Journal of Microbiology and Biotechnology
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• v.27 no.2
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• pp.277-288
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• 2017

Rhizomucor miehei NRRL 5282 and Rhizopus oryzae NRRL 1526 can produce lipases with high synthetic activities in wheat bran-based solid-state culture. In this study, the purification and biochemical characterization of the lipolytic activities of these lipases are presented. SDS-PAGE indicated a molecular mass of about 55 and 35 kDa for the purified R. miehei and Rh. oryzae enzymes, respectively. p-Nitrophenyl palmitate (pNPP) hydrolysis was maximal at $40^{\circ}C$ and pH 7.0 for the R. miehei lipase, and at $30^{\circ}C$ and pH 5.2 for the Rh. oryzae enzyme. The enzymes showed almost equal affinity to pNPP, but the $V_{max}$ of the Rh. oryzae lipase was about 1.13 times higher than that determined for R. miehei using the same substrate. For both enzymes, a dramatic loss of activity was observed in the presence of 5 mM $Hg^{2+}$, $Zn^{2+}$, or $Mn^{2+}$, 10 mM N-bromosuccinimide or sodium dodecyl sulfate, and 5-10% (v/v) of hexanol or butanol. At the same time, they proved to be extraordinarily stable in the presence of n-hexane, cyclohexane, n-heptane, and isooctane. Moreover, isopentanol up to 10% (v/v) and propionic acid in 1 mM concentrations increased the pNPP hydrolyzing activity of R. miehei lipase. Both enzymes had 1,3-regioselectivity, and efficiently hydrolyzed p-nitrophenyl (pNP) esters with C8-C16 acids, exhibiting maximum activity towards pNP-caprylate (R. miehei) and pNP-dodecanoate (Rh. oryzae). The purified lipases are promising candidates for various biotechnological applications.

• Korean Journal of Environmental Biology
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• v.41 no.4
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• pp.677-682
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• 2023

Milky white spots appeared on red bean leaves in a red bean cultivation area located in Jangyeon-myeon, Goesan-gun, Chungbuk Province. After culturing the pathogen in PDA medium, their morphology was observed, and their genes were BLAST-searched in the National Center for Biotechnology Information (NCBI). The pathogen was identified as a fungus called Rhizopus arrhizus. As a result of reinoculating the isolated pathogen on red beans, the same symptoms as those in the isolated leaves occurred. Characteristic colonies of R. arrhizuson PDA medium initially showed a bright color and then changed to dark gray over time, with mostly spherical sporangia. The sporangiospores were spherical or elliptical, mostly irregular, and small in size. Therefore, based on these results, this disease has not yet been reported in red beans and was called red bean brown leaf blight caused by Rhizopus arrhizus A. Fisch (syn. R. oryzae).

• 한국균학회소식:학술대회논문집
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• 2015.05a
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• pp.61-61
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• 2015

Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is one of the most destructive diseases of rice worldwide. The rice - M. oryzae pathosystem has become a model in the study of plant - fungal interactions due to its economic importance and accumulating knowledge. During the evolutionary arms race with M. oryzae, rice plants evolved a repertoire of Resistance (R) genes to protect themselves from diseases in a gene-for-gene fashion. M. oryzae secretes a battery of small effector proteins to manipulate host functions for its successful infection, and some of them are recognized by host R proteins as avirulence effectors (AVR), which turns on strong immunity. Therefore, the analysis of interactions between AVRs and their cognate R proteins provide crucial insights into the molecular basis of plant - fungal interactions. Rice blast resistance genes Pik, Pia, Pii comprise pairs of protein-coding ORFs, Pik-1 and Pik-2, RGA4 and RGA5, Pii-1 and Pii-2, respectively. In all three cases, the paired genes are tightly linked and oriented to the opposite directions. In the AVR-Pik/Pik interaction, it has been unraveled that AVR-Pik binds to the N-terminal coiled-coil domain of Pik-1. RGA4 and RGA5 are necessary and sufficient to mediate Pia resistance and recognize the M. oryzae effectors AVR-Pia and AVR1-CO39. A domain at the C-terminus of RGA5 characterized by a heavy metal associated domain was identified as the AVR-binding domain of RGA5. Similarly, physical interactions among Pii-1, Pii-2 and AVR-Pii are being analyzed.

• 한국균학회소식:학술대회논문집
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• 2014.05a
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• pp.25-25
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• 2014

Koji molds are comprised of yellow, black and white. Black and white koji molds were recently re-visited by this author and it is concluded that they consists of Aspergillus luchuesnsis, A. niger and A. tubingensis, and the most important species for alcoholic beverage production is A. luchuensis. In the case of yellow koji mold, it is comprised of Aspergillus oryzae, A. sojae and A. tamari. In the case of A. sojae, the species is scarcely isolated from nature and rarely used for industry in Korea. Aspergillus tamari is often isolated from traditional Korean Meju, a fermented soybean product, and the classification of the species is clear. However, in the case of A. oryzae, differentiation between A. oryzae and A. flavus is still in controversy. In this study, we collected 415 strains of Aspergillus flavus/oryzae complex from air, rice straw, soybean, corn, peanut, arable soil and Meju in Korea and we examined the aflatoxin producing capacity of the strains. The norB-cypA, omtA and aflR genes in the aflatoxin biosynthesis gene cluster were analyzed. We found that 367 strains (88.4%) belonged to non-aflatoxigenic group (Type I of norB-cypA, IB-L-B-, IC-AO, or IA-L-B- of omtA, and AO type of aflR), and only 48 strains (11.6%) belonged to aflatoxin-producible group (Type II of norB-cypA, IC-L-B+/B- or IC-L-B+ of omtA, and AF type of aflR). In the case of A. flavus/oryzae strains from Meju, almost strains (178/192, 92.7%) belonged to non-aflatoxigenic group and only 14 strains (7.3 %) belonged to aflatoxin-producible group. It is proposed in this study that non-aflatoxigenic strain from Meju is classified as A. oryzae, considering that Meju is food material.

• The Korean Journal of Mycology
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• v.23 no.1 s.72
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• pp.86-91
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• 1995

Isoenzymatic analysis related with cadmium adaptation and detoxifying mechanism were carried out upon Rhizopus oryzae. When cadmium was added into R. oryzae culture, activities of malate dehydrogenase (MDH) and glucose phosphate isomerase (GPI) related with carbohydrate metabolizing pathways were stimulated. Novel isoenzyme CAT-2 related with removing intracellular toxic peroxides, was induced lately and derepressed very highly. On the other hand, lactate-catabolizing enzymes such as lactate dehydrogenase (LDH) and alcohol dehydrogenase (ADH) were repressed. These results strongly suggest that, under cadmium stress, much of derepression of enzymes relating with central metabolism such as TCA cycle that produces high yield of energy and relating with removal of toxic peroxides should be necessary.