Diversity, Saccharification Capacity, and Toxigenicity Analyses of Fungal Isolates in Nuruk

Min Sik Kim1   Sinil Kim1   Byeong-Seok Ha1   Hye-Young  Park3   Seong-Yeol BaeK3   Soo-Hwan Yeo3   Hyeon-Su Ro123   


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±21.6 (×104), 1,868.0±27.7 (×104), and 775.1±19.2 (×104) 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 β-glucan in crop component of Nuruk since R. oryzae was the only fungus that showed β-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.


본 연구는 농촌진흥청 공동연구사업(Project No. PJ00999304)의 지원에 의해 이루어진 것이며, 김민식, 김신일, 하병석은 BK21 프로그램의 장학금을 지원받았습니다.

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