• 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%).

• 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.

• 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.

• The Korean Journal of Mycology
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• v.39 no.1
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• pp.78-84
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• 2011

To develop new functional traditional rice wines using Gugija and Liriope tuber as raw materials, screenings of optimal fungal nuruk and alcohol fermentative yeast for brewing of Gugija-L. tuber traditional rice wine were performed with investigation of optimal fermentation condition. Finally, we selected commercial SJ nuruk and Saccharomyces cerevisiae C-2 as optimal nuruk and yeast for Gugija-L. tuber traditional rice wine. Furthermore, a new antihypertensive and anti-gout Gugija-L. tuber traditional rice wine was produced when 3% of Jangmyong Gugija and L. tuber No.1 were added into cooked rice and then fermented at $25^{\circ}C$ for 5 days with SJ nuruk and S. cerevisiae C-2.

• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.4
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• pp.789-799
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• 1998

Literatures on microorganisms of traditional Korean nuruk published since 1945 were reviewed in this paper. Traditional Korean nuruk consists of raw barley and various grains. Traditional Korean nuruk consists of unbolied raw barely and various grains. They are ground to paste and moistened, and then naturally inoculated by airborne microorganisms. Therefore, many kinds of microorganisms such as fungi, yeast, and bacteria grwo in nuruk. Since 1945, new 14 species of Aspergillus and 9 species of Penicillium have been identified from traditional Korean nuruk. Total number of fungal species identified so far is now up to 38 species among 12 different genus. Among newly isolated fungal species, Aspergillus penicilloides and Penicillium, expansum showed not only high production rate of acid and amylase but also extreme stability of the enzyme at room temperature for 3 months. As examples of newly isolated yeast species, there are 5 species of Candida, 4 species of Hansenula, 1 species of Pichia and 1 species of Schizosaccharomyces. Total number of yeast species isolated so far is up to 18 species from different 8 genus. Newly isolated bacteria, were Bacillus pumilus, Lactobacillus casei and Leuconostoc mesenteroides.

• Journal of Microbiology and Biotechnology
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• v.23 no.1
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• pp.40-46
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• 2013

A variety of nuruk were collected from various provinces in Korea, and their microflora profiles were analyzed at the species level. A total of 42 nuruk samples were collected and when the viable cell numbers in these nuruk were enumerated, the average cell numbers of bacteria, fungi, yeast, and lactic acid bacteria from all nuruk were 7.21, 7.91, 3.49, and 4.88 log CFU/10 g, respectively. There were no significant differences in viable cell numbers of bacteria or fungi according to regions collected. Bacillus amyloliquefaciens and B. subtilis were the predominant bacterial strains in most samples. A significant portion, 13 out of 42 nuruk, contained foodborne pathogens such as B. cereus or Cronobacter sakazakii. There were various species of lactic acid bacteria such as Enterococcus faecium and Pediococcus pentosaceus in nuruk. It was unexpectedly found that only 13 among the 42 nuruk samples contained Aspergillus oryzae, the representative saccharifying fungi in makgeolli, whereas a fungi Lichtheimia corymbifera was widely distributed in nuruk. It was also found that Pichia jadinii was the predominant yeast strain in most nuruk, but the representative alcohol fermentation strain, Saccharomyces cerevisiae, was isolated from only 18 out of the 42 nuruk. These results suggested that a variety of species of fungi and yeast were distributed in nuruk and involved in the fermentation of makgeolli. In this study, a total of 64 bacterial species, 39 fugal species, and 15 yeast species were identified from nuruk. Among these strains, 37 bacterial species, 20 fungal species, and 8 yeast species were distributed less than 0.1%.

• The Korean Journal of Mycology
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• v.30 no.1
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• pp.61-65
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• 2002

The objectives of this study were to find the nuruk fungal isolate for Korean traditional rice wine and to compare the tastes of rice wines made with its single inoculum. The fungal isolates including the species of Absidia, Mucor, Rhizopus and Aspergillus were used for Korean traditional rice-wine production. The four species were cultured and measured for productions of amylase under various water contents. The four different species tested were different in their growth under the rice cereals with different moisture contents; the species of Absidia and Rhizopus grew better compared to the other species under the lower moisture conditions. The tastes and alcohol concentrations of the rice-wines made with each different inoculum were compared with those of commercial rice wines made with traditional method. As a result, it was speculated that the traditional rice wines were made with nuruk, which is mainly composed of Zygomycetous fungi, such as Absidia, Mucor, and Rhzopus. Also, it was strongly suggested that the traditional nuruk might not be a source of amylase, but a source of fungal inoculum.

• 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.26 no.5
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• pp.759-766
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• 1997

From Nuruks, a traditional Korean starter for rice wine, collected from 42 different areas in Korea, 111 fungal strains were isolated. These isolates were identified as 25 species belonging to seven genera of Rhizopus oryzae(14 strains), R. oligosporus(8 strains), R. nigricans(5 strains), R. arrhizus (5 strains), Aspergillus oryzae(12 strains),Asp. parasiticus(8 strains), Asp. fumigatus(3 strains), Asp. ochraceus(7 strains), Asp. wentii(5 strains), Asp. parasiticus(8 strains), Asp. penicilloides(3 strains), Asp. clavatus(4 strains), Penicillium purpurogenum(2 strains), Pen. glabrum(1 strain), Pen. granulaturm (1 strsin), Pen. fellutanum(1 strain), Geotrichum candidum(2 strains), Absidia corymbifera(12 strains), Mucor racemosus(2 strains), M. plumbeus(2 strains) and Curvularia lunatus(3 strains).

• The Korean Journal of Mycology
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• v.36 no.1
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• pp.1-8
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• 2008

To investigate the mycoflora of indoor air in a Sogokju, traditional rice wine, factory, fungi were sampled and analyzed from the air of several rooms in the factory using an Anderson air sampler and from two kinds of Nuruk. Twelve fungal species belonging to the genera of Aspergillus, Penicillium, Gibberella, Cladosporium, and Talaromyces were isolated. Species belonging to Aspergillus and Penicillium genera were the major species. Seven different species of Penicillium were isolated from each different room of the factory. The Aspergillus species found from indoor air of the factory was also found from Nuruk. Rhizopus sp. was commonly isolated from Nuruk but not from indoor air of the factory. This is first report of fungi present in indoor air of a traditional rice wine factory in Korea.