Transformation of 12-deoxycardenolids with Streptomyces purpurascens

Streptomyces purpurascens transforms primary and secondary 12-deoxycardenolids into digoxin, 7 beta-hydroxy-digitoxin and 7 beta-hydroxy-digoxin, respectively. A metabolic pathway is proposed for cardenolid transformations and the enzymes participating in it are investigated. The substrate concentration in the medium can be increased by using a water-miscible solvent of electron donor character. The newly developed procedure yields 0.5 g/1(-1) of digoxin in a five-day fermentation.