Effects of <i>Aspergillus oryzae</i> -derived rice- <i>koji</i> protein on the sake metabolome

Rice-koji plays a crucial role in sake brewing. Although some functions of <i>Aspergillus oryzae</i>-derived proteins have been elucidated, most remain poorly understood. In this study, we identified rice-koji proteins (RKPs) via proteomic analysis and investigated their effects on sake composition using gene disruption strains. Analyses of samples from rice-koji preparation and small-scale sake brewing showed that disruption of rkp genes altered <i>A. oryzae</i> growth and modified multiple sake component profiles. Notably, rkp genes that influenced fungal biomass in rice-koji were also associated with significant changes in sake composition. These findings reveal the diverse contributions of <i>A. oryzae</i> to sake brewing and enhance our understanding of the fermentation potential of filamentous fungi, with potential applications in other fermentation-based industries.