Abstract
Various strains of Aspergillus oryzae, regarded as a domesticated variant of aflatoxigenic Aspergillus flavus, are utilized in soybean fermentation industry of Korea. This study compared A. oryzae/flavus strains isolated from various environments in Korea, including industrial settings, Meju (brick of dried fermented soybeans), and wild conditions, with globally reported strains using genomic analysis to determine their taxonomic positions and safety. Using population genomics, five distinct groups (A to E) were identified, with all aflatoxigenic Korean strains in Group C and non-aflatoxigenic Korean strains in Groups A, B, and E. Korean strains from Meju and wild conditions are distributed across Groups A and B, and most of the Korean industrial strains form a sub-cluster with Japanese industrial strains in Group A. Comparing secondary metabolite gene cluster mutation pattern, three gene clusters (Aflatoxin, Cyclopiazonic acid and Ditryptophenaline) were revealed as group specific ones. In aflatoxin and cyclopiazonic acid clusters, most of the Group C strains had intact regions compared to other groups strains.Since most of the Group C strains produce aflatoxin and have intact Aflatoxin and Cyclopiazonic acid gene cluster, we considered that this group represent A. flavus. Profiling of MALDI-TOF MS analysis also distinguished Group C from Groups A, B and E by specific proteomic peaks. Among these peaks, those around 12700 to 12900 m/z (Da) are expected to correspond to AflF (nor B), an enzyme involved in Aflatoxin metabolism. These results showed taxonomic positions of Korean strains of A. oryzae/ flavus from various environments and also showed possibility to differentiate between A. oryzae and A. flavus with genome and Maldi-tof analysis.