PURPOSE:A microorganism capable of producing putrescine oxidase is cultured and the putrescine oxidase is collected from the culture mixture with improvement in complication for the enzyme preparation and high Km value. CONSTITUTION:A microorganism in Nocardia capable of producing putrescine oxidase such as Nocardia erythropolis, is cultured in a medium containing putrescine, preferably in a liquid medium aerobically. As the nutrients for the culture medium, are used common ones which are usually used to culture microorganisms. As a carbon source is used an assimilable carbohydrate such as glucose, molasses, or glycerol. The nitrogen source is, e.g., pepton, yeast extract, meat essence or ammonium sulfate. Preferably, putrescine or spermidine is added as the nitrogen source to increase the capability of putrescine oxidase production on culturing.
