The cerulenin-producing strain has some unique characteristics: it forms aerial hyphae and conidiophore when applied on Czapek agar as shown in Fig. 1 and Fig. 2, respectively, and it forms bluish-green aerial mycelium on malt agar. It has thus been classified as genus Cephalosporium and accordingly named Cephalo-sporium caerulens (49).

The production of cerulenin was originally performed under cultural conditions of 27 to 32TC by using glucose and glycerol as carbon sources and peptone and corn steep liquor as ni-trogen sources (50). Unfortunately, however, it was found that helvolic acid andsteroidal antibiotics (Fig. 3) were produced predominantly over cerulenin under these conditions. Such difficulties precluded the usefulness of this method for efficient production of cerulenin. Meanwhile, because much attention began to be paid to its specific mode of actionas an inhibitor of lipid biosynthesis, a method was needed to improve the yield of cerulenin. As a matter of course, the condition of fermentative production of the antibiotic that was originally reported was reexamined. As a beginning step to do so, the antimicrobial activities of cerulenin and helvolic acid were reevaluated. Among the microorganisms listed, Candida albicansKF-1 and Corynebac-terium paurometablum KB-121 were chosen as the most appropriate test microorganisms for the selective bioassay of cerulenin and helvolic acid, respectively (36). Attempts were subsequently made to investigate the medium for the selective production of cerulenin. Although a previously employed production medium (50) that contained 6.0% glu-cose, 0.5% peptone, 0.3% NaCl, and 0.3% CaCO3 afforded mostly helvolic acid (350, tg/ml) and a small amount of cerulenin (50, tg/ml), further study revealed that a more suitable medium for the efficient production of cerulenin should contain 1% glucose, 3% glycerol, 0.5% peptone, and 0.2% NaCl. By using this produc-681