Nuruk samples collected from various regions in Korea were investigated in terms of fungal contents and diversity. Measurement of colony forming unit (CFU) in the nuruk suspensions on DRBC agar revealed that the nuruk samples, MS4, MS8, and MS10, were among the highest fungal density by showing 1.27...
Nuruk samples collected from various regions in Korea were investigated in terms of fungal contents and diversity. Measurement of colony forming unit (CFU) in the nuruk suspensions on DRBC agar revealed that the nuruk samples, MS4, MS8, and MS10, were among the highest fungal density by showing 1.2789±21.6 (x107), 1.8680±27.7 (x107), 0.7751±19.2 (x107) CFU per 20 mg nuruk, respectively. The majority of the 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 the measurement of amylase activity in the culture broth. The amylase activity was the highest in A. niger and A. luchuensis followed by S. fibuligera. A. oryzae and R. oryzae showed fair amylase activities but significantly lower than the three fungal species. R. oryzae was suggested to play an additional role in the degradation of β-glucan in crop component of nuruk since R. oryzae was the only fungus that shows the β-glucanase activity among the fungal isolates. Aflatoxigenicity of the isolated Aspergilli to confirm the safety of the nuruk was estimated using the DNA makers including norB-cypA, aflR, and omtA. All the isolates were 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
Nuruk samples collected from various regions in Korea were investigated in terms of fungal contents and diversity. Measurement of colony forming unit (CFU) in the nuruk suspensions on DRBC agar revealed that the nuruk samples, MS4, MS8, and MS10, were among the highest fungal density by showing 1.2789±21.6 (x107), 1.8680±27.7 (x107), 0.7751±19.2 (x107) CFU per 20 mg nuruk, respectively. The majority of the 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 the measurement of amylase activity in the culture broth. The amylase activity was the highest in A. niger and A. luchuensis followed by S. fibuligera. A. oryzae and R. oryzae showed fair amylase activities but significantly lower than the three fungal species. R. oryzae was suggested to play an additional role in the degradation of β-glucan in crop component of nuruk since R. oryzae was the only fungus that shows the β-glucanase activity among the fungal isolates. Aflatoxigenicity of the isolated Aspergilli to confirm the safety of the nuruk was estimated using the DNA makers including norB-cypA, aflR, and omtA. All the isolates were 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
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#Nuruk Diversity Saccharification Toxigenicity
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