Wild toxicity, cultivated safety: aflatoxin and kōji classification as knowledge infrastructure

ABSTRACT In 1960, the trajectory of aflatoxin as one of the earliest and best studied cases of a naturally occurring carcinogen in food intersected with the trajectory of an industrial microbe known in the Japanese vernacular as kōji, used for centuries in Japan to make sake, soy sauce, and miso. Over about two decades, the aflatoxin crisis spurred the emergence of a new evolutionary narrative of kōji, Aspergillus oryzae, as a domesticated, non-toxigenic species unique to the Japanese brewery that was clearly distinguishable from its wild, commonly found in nature, and aflatoxin-producing close relative, Aspergillus flavus. It was a shift that came hand-in-hand with the reconstruction of kōji classification. This essay examines the challenges of microbial classification after 1960. By asking how mycologists made a scientific narrative that originated in the interests of Japanese national industries convincing internationally, it explores the knowledge infrastructure that underlay both manufacturing issues and knowledge in microbiology.