Antioxidant production by the katsuobushi mold Aspergillus chevalieri revealed—using fermentation-mimicking solid cultures
摘要
Katsuobushi molds are fungi involved in the fermentation of dried bonito, and most of them belong to the genus Aspergillus. Aspergillus fungi can biosynthesize various secondary metabolites, and katsuobushi molds may produce bioactive compounds during fermentation. Although previous studies have reported that katsuobushi molds produce bioactive compounds, these studies used agar-based media to culture the fungi. There are important differences between agar-based culture and dried bonito fermentation conditions, but there is limited information on secondary metabolite production by katsuobushi molds during dried bonito fermentation. In this study, katsuobushi molds were cultured in model culture systems that mimicked real dried bonito fermentation conditions. A katsuobushi mold, Aspergillus chevalieri strain JCM23047, was cultured on bonito meat and dried bonito powder, and the antioxidant neoechinulin C was identified in both cultures. Furthermore, neoechinulin C was detected in commercially available fermented dried bonito. These results suggest that neoechinulin C is produced by katsuobushi molds on the surface of dried bonito and acts as a preservative owing to its antioxidant activity. To our knowledge, this is the first report of a bioactive compound originating from commercially available fermented dried bonito. This study provides insight into the function of katsuobushi molds during dried bonito fermentation.