The antimycoticum ambruticin was produced by cultivating the myxobacterium Sorangium cellulosum in shake flasks and stirred tank reactors with 10- and 30-l working volumes. During growth and product formation amino acid concentrations in the complex media were measured by HPLC. In the logarithmic growth phase free aspartate and glutamate were assimilated without product formation. After consumption of aspartate and glutamate, growth was limited and ambruticin production set in. The effects of biological parameters such as age, amount of inoculum, pretreatment of cells before inoculation and time of precultivation were also investigated.