Analysis of aflatoxin biosynthetic pathway gene cluster of Aspergillus oryzae RIB strains

抄録

Koji mold, Aspergillus oryzae has been used in the traditional fermentation industry for sake, shoyu (soy sauce), miso and other beverages and foods, and its safety is proved historically. However, A. oryzae taxonomically related to aflatoxin (AF) producer A. flavus and some strains possess the entire AF biosynthetic pathway gene cluster. In case of using A. oryzae in food processing, it is desirable to select the strains which do not possess AF biosynthetic genes. The simple method which can confirm the presence of these genes is needed to select these strains. In this study, we designed PCR primers which specifically amplify AF biosynthetic genes and analyzed the presence of these genes in 210 RIB strains (A. oryzae culture collection in NRIB). The classification and the characteristic evaluation of these strains were also examined. From results of PCR amplification patterns of these genes, RIB strains were classified into four groups, but most of the strains were classified into main two groups. Group 1 conserves AF biosynthetic gene cluster entirely (122 of 210 strains, 58.1 %) and group 2 possesses a part of its cluster which is from vbs to avnA (76 of 210, 36.2 %). The differences between group 1 and group 2 on mycological characters were recognized statistically in length of stalk, production of kojic acid, and so on.