Production of cordycepin by surface culture using the medicinal mushroom Cordyceps militaris

The production conditions of cordycepin (3′-deoxyadenosine), which is a kind of nucleoside analogue, were investigated by a surface culture using Cordyceps militaris NBRC 9787. About 98% of the cordycepin synthesized by Cordyceps militaris was secreted into the culture medium, and other nucleic acid-related compounds except for cordycepin and guanine were only slightly observed in the medium. The preferable nitrogen source for the cordycepin production was the mixture of peptone and yeast extract, in which the ratio of the yeast extract was 75% or greater. The optimal carbon/nitrogen ratio (w/w) was 2/1 when glucose was used as the carbon source. The lower medium depth resulted in a higher productivity over the present experimental range from 1.8 to 5.3 cm. Under the optimal conditions, the maximum cordycepin concentration in the culture medium reached 640 mg/l, and the maximum cordycepin productivity was 32 mg/(l·day).