Enhancement of cerulenin production by a natural zeolite, an ammonium ion-trapping agent.

Addition of a natural zeolite, a known ammonium ion-trapping agent, to a complex medium resulted in a several fold increase in cerulenin production by Cephalosporium caerulens. In the presence of zeolite, ammonium ion in the medium decreased, while mycelial growth increased to a small extent, and pH values remained constant. Small amounts of ammonium bicarbonate inhibited cerulenin production without affecting mycelial growth and pH values. It is thus assumed that zeolite stimulated cerulenin production by releasing the biosynthesis from the suppression by ammonium ions in C. caerulens.