Cephalosporin C was produced by Acremonium chrysogenum in a stirred tank reactor in fed-batch operation in six different complex cultivation media by using the same composition: with 30 and 50% dilution and 150 and 200% enrichment of the reference 100% medium. The concentrations of the medium components, the β-lactam precursors and the product were monitored during cultivation. The concentrations, the productivity and the yield coefficients of cephalosporin C were determined. With regard to the yield coefficient the 50% medium and with respect to the productivity the 150% medium seems to be the most economical system. The results of the regulation of CPC production are at odds with previous findings with more primitive strains.