• 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 the East Asian Society of Dietary Life
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• v.22 no.1
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• pp.103-108
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• 2012

Nuruk is a fermented ingredient used for production of traditional Korean rice wine. In this study, quality characteristics of mixed-grain nuruk was made by brewing with different fungal strains was analyzed. Quality elements including enzyme activity and organic acids constituents were measured. The fermentation time of the nuruk did not make a significant difference in terms of its pH, but the acidity and amino acid content for nuruk made from a mixture of two fungal strains was higher than that seen with a single fungal strain. Overall, the enzyme activity for two fungal strain nuruk was higher than that observed for single fungal strain nuruk, with ${\alpha}$-amylase and acidic protease activity in the mixed strain nuruk observed to be more than twice that of the single strain. The major organic acids observed in the manufactured nuruk were identified as acetic, citric, formic, fumaric, lactic, malic and oxalic acids. The total amount of organic acids contained in the nuruk made with the two fungal strain was (2,116.3 mg%). The fungal strains used were A. kawachii SC60 nuruk (1,608.5 mg%) and A. oryzae RIB1353 nuruk (1,146.7 mg%).

• Korean Journal of Microbiology
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• v.8 no.2
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• pp.69-76
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• 1970

1. The yeasts in the two samples of Nuruk (mold wheat) which one prepared at the College of Agriculture, Choong-Nam University (S) and the other purchased at a market(T), were examined and counted. The yeasts were differe entiated by the market (T), were examined and counted. The yeasts were differe entiated by the TTC(2,3,5-triphenyltetrazolium chloride)agar overlay technique that yields a varied shade of color. The results were : the population of yeasts in 1g of Nuruk S was about $6{\times}10^4$, 56.5% of which were TTC-pink yeasts, 16% TTC-red pink yeasts, 8% were TTC-red yeasts, and 16.5% TTC-white yeasts. In Nuruk T(1g), the number of yeasts accounted for $14{\times}10^4$ and constituted of 42% TTC0pink, 21% TTC-red pink, 23% TTC-red and 9% TTC-white. 2. During the fermentation of Takju (Korean Sake) employing the Nuruk S and T the yeast flora throughout the brewing were observed in 12 hour intervals. TTC pink and red yeasts considered to be the major yeasts were isolated all cultured. The strains ($1{\times}10^5$/ml) were added to the mashes S and T in which pH was adjusted to 4.2 and the change of yeast flora was examined during fermentation.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.12
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• pp.1785-1791
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• 2012

This study aimed to characterize and compare makgeolli (a Korean rice wine) made using different raw materials. Five cultivars of rice and wheat flour were used as starch materials for makgeolli and assessed for their moisture, crude lipid, crude protein, and crude dietary fiber content. Overall, wheat flour was higher in crude lipid and crude protein and lower in moisture than rice. Makgeolli characteristics were assessed for pH, total acids, organic acids, free sugars, color and appearance. We found no significant differences in pH and total acids between makgeolli made from rice and wheat flour. In addition, the major free sugar in the makgeolli made from rice and wheat flour was glucose, although the content of total free sugars was lower in the wheat flour makgeolli (67.75 mg/mL) than the rice makgeolli (76.41~84.53 mg/mL). In terms of organic acids content, the total organic acid content was highest in the wheat flour makgeolli, while the major organic acids of the makgeolli made from rice and wheat flour were lactic acid and succinic acid, respectively. There were no significant differences in color values among rice makgeolli, but the rice makgeolli was higher in sensory scores (indicating preference) than the wheat flour makgeolli. As the degree of milling increased, moisture, crude lipid, and crude protein in the rice decreased. Acetic acid in the makgeolli also decreased, while there were no significant differences in pH, total acids, free sugars, color values, and sensory scores (except fruitiness). Traditional nuruk (TN) and cultured nuruk (CN) were compared as fermentation starters. Nuruk is a Korean traditional starter for fermentation of makgeolli and a raw material for makgeolli making. The pH in the makgoelli made with TN and CN were 4.29~4.65 and 4.02~4.23, respectively. Total organic acid content was higher in the TN makgeolli (3.5~6.3 mg/mL) compared to the CN makgeolli (2.3~4.3 mg/mL). The content of free sugars in the makgeolli made with CN was higher (59.44~73.34 mg/mL) than that with TN (56.45~59.75 mg/mL). The Hunter color test showed that makgeolli made with TN was lighter and higher in red and yellow color compared to CN. Overall sensory acceptability was higher in the CN makgeolli compared to the TN makgeolli.

• 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.

• 한국균학회소식:학술대회논문집
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• 2015.11a
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• pp.11-11
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• 2015

A total of sixty-six samples of Nuruk, a fermention starter used to make the Korean traditional rice wine, Makgeolli, were collected from central and southern regions of Korea in 2013 and 2014. We classified two groups of the Nuruk samples, "commercial" and "home-made", according to the manufacturing procedure and purpose of use. Commercial Nuruks were made in a controlled environment where the temperature and humidity are fixed and the final product is supplied to Makgeolli manufacturers. Home-made Nuruks were made under uncontrolled conditions in the naturally opened environment and were intended for use in the production of small amounts of home-brewed Makgeolli. We obtained more than five hundred isolates including filamentous fungi and yeasts from the Nuruk samples followed by identification of fungal species. Also we stored glycerol stocks of each single isolate at $-70^{\circ}C$. We identified the species of each isolate based on the sequences of ITS regions amplified with two different universal primer pairs. We also performed morphological characterization of the filamentous fungi and yeast species through observations under the microscope. We investigated the major fungal species of commercial and home-made Nuruks by counting the colony forming units (CFU) and analyzing the occurrence tendency of fungal species. While commercial Nuruks contained mostly high CFU of yeasts, home-made Nuruks showed relatively high occurrence of filamentous fungi. One of the representative Nuruk manufacturers used both domestic wheat bran and imported ones, mainly from US, as raw material. Depending on the source of ingredient, the fungal diversity was somewhat different. Another commercial Nuruk sample was collected twice, once in 2013 and again in 2014, and showed different diversity of fungal species in each year. Nuruks obtained from the southern regions of Korea and Jeju island showed high frequency of yeast such as Saccharomycopsis fibuligera and Pichia species as well as unique filamentous fungus, Monascus species. S. fibuligera was easily found in many Nuruk samples with high CFU. The major filamentous fungi were Aspergillus, Lichtheimia, Mucor and Penicillium species. In order to further our understanding of the isolates and their potential industrial applications, we assayed three enzymes, alpha amylase, glucoamylase and acid protease from 140 isolates out of about five hundred isolates and selected about 10 excellent strains with high enzyme activities. With these fungal isolates, we will perform omics analyses including genomics, transcriptomics, metabolic pathway analyses, and metabolomics followed by whole genome sequencing of unique isolates associated with the basic research of Nuruk and that also has applications in the Makgeolli making process.

• Microbiology and Biotechnology Letters
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• v.40 no.4
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• pp.319-324
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• 2012

Production of liquid starters using wheat bran as a medium for Rhizopus oryzae N174 and the changes in their characteristics noted during storage were investigated in this study. The optimal culture conditions of the liquid starters were determined to be 5~15% (w/v) wheat bran and 48~72 hrs of incubation. The effects of liquid starters with different storage periods and temperatures (-18, 4, 10 and $25^{\circ}C$) on the quality of wheat nuruk were evaluated. According to the results of the pH, acidity, reducing sugar and enzyme activities, it was found that liquid starter using wheat bran preserved for one day, at any temperature, is the best method of storage for seed cultures for R. oryzae N174.

• Journal of the East Asian Society of Dietary Life
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• v.1 no.2
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• pp.133-149
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• 1991

The contents of“Joo-chan”consist of eighty two items about alcoholics, a number of side dishes and soybean sauces. Interpreted content was classified and analyzed. Selected 52 items among those brewages, artless-brewing alcoholics, were distributed into 6 large patterns. The materials used for brewing artless alcoholics were regular rice, waxy rice, wheat and yeast(NURUK). Six patterns, grounded on these materials, were set one thing to another and analyzed.

• Journal of the East Asian Society of Dietary Life
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• v.2 no.1
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• pp.1-16
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• 1992

The contents of "Joo-Chan" consist of eighty two items abut alcoholics, a number of side dished and soybean sauces. Interpreted content was classified and analyzed. Selected 31 items among those brewages, compounded alcoholics, were distributed into 7 large patterns. The materials used for compounded alcoholics, were regular rice, waxy rice, wheat, yeast(NURUK), and compounded extra materials. Seven patterns, grounded on those materials, were set one thing to another and analyzed. analyzed.

• Korean journal of food and cookery science
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• v.28 no.4
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• pp.383-390
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• 2012

In order to reproduce Sanghwabyung that people in the past made and ate at Yuduil (June 6th by lunar calendar) among our traditional rice cakes, this study manufactured Sanghwabyung with black wheat flour by adding the wheat bran and Nuruk powder as leavening source, according to the old cook book "Gyuhapchongseo" and analyzed the quality characteristics. As a result of total phenol and flavonoid contents, DPPH radical scavenging activity of black wheat contents showed the gradual increase significantly (p < 0.001). The number of lactic acid bacteria was $6.72{\times}10^7$ CFU/mL just after preparation, and the number of yeast was $5.59{\times}10^7 $ CFU/mL. The number of lactic acid bacteria and yeast increased after 24 h to $8.48{\times}10^7$ CFU/mL and $5.40{\times}10^7$ CFU/mL. Hard-ness was the lowest in WF30%, compared with the C and the highest in BF100% and WF100%. The more the added portion increased in WF30% and BF30%, the more the hardness increased significantly (p < 0.001). The cohesiveness was the highest in WF30%, compared with C and BF30%, the lowest. It was shown significantly different between the C and WF and BF sample groups (p < 0.01). Springiness was the highest in WF10% and WF50%, compared with that in C and BF100%, which were the lowest. Springiness decreased significantly (p < 0.001) ad-ded portion increased between WF30% and BF30%. Gumminess was the highest in BF100% and WF100%, whereas that of WF20% was the lowest (p < 0.001). Chew-iness was the highest in BF100% and WF100% (p < 0.001).