Aspergillus oryzae, a useful industrial filamentous fungus, produces limited varieties of secondary metabolites, such as kojic acid. Thus, for the production of valuable secondary metabolites by genetic engineering, the species is considered a clean host, enabling easy purification from cultured cells. | Use of the kojA promoter, involved in kojic acid biosynthesis, for polyketide production in Aspergillus oryzae: Implications for longterm production