Abstract
Neurospora sp. ATCC 46892 grew on pregelatinized polished rice, even as a sole carbon source, and simultaneously produced a strong fruity odor. The main components of the aroma were ethyl caproate, ethanol and isoamyl alcohol, as judged on gas chromatography. The effects of carbon or nitrogen sources and impregnating nutritive solutions on ethyl caproate production were examined, and the optimum conditions for the ester production were determined, under which more ethyl caproate, which is responsible for the fruity odor, and less isoamyl alcohol were produced than in a liquid culture. The cell-free extract of the solid state culture (which we call N-koji) contained a strong alcohol acyltransferase activity, which caused abundant ethyl caproate production in the culture. The odoriferous N-koji was applied to the making of sake, a Japanese alcoholic beverage, and as a result a sake rich in ethyl caproate was obtained. It was suggested that the solid-state culture was one of the useful methods for fruity odor formation.
