Observation of novel internal structures within sclerotia of industrial Aspergillus oryzae strains

This study explored sclerotia-forming strains from industrial Aspergillus oryzae strains, focusing on factors contributing to sclerotial morphological diversity. Using rice bran medium, ten MAT1-1 industrial strains capable of producing sclerotia were newly identified. Phylogenetic analysis revealed that strains in the specific clade are particularly prone to sclerotia formation under the conditions tested. Controlled environmental conditions, including specific CO₂ concentrations and incubation periods, facilitated the development of novel internal structures that have not been previously reported in A. oryzae. Although these internal structures resemble ascocarps found in other Aspergillus species, no evidence related to reproduction was identified. Further studies are necessary to elucidate the roles of these internal structures. The findings of this study provide a foundation for future research into the cryptic sexual reproduction of A. oryzae.