Control of ammonium ion level for efficient nanaomycin production.

The addition of a small amount of NH4+ to a complex medium increased nanaomycin production by Streptomyces rosa subsp. notoensis OS-3966. The best NH4+ donor for nanaomycin production was NH4+-saturated natural zeolite, with which the maximum titer of nanaomycin E was 760 micrograms/ml, about four fold higher than the control titer. In contrast, lowering NH4+ levels by adding NH4+-trapping agents such as untreated natural zeolite reduced antibiotic production.