In this work, cephalosporin C (CPC) production on pilot scale fermenters of 600 1 capacity with 350 1 working volume by Acremonium chrysogenum EMCC 904 was performed. The effects of fermentation medium composition, inoculum concentration, initial pH and aeration rate on CPC production by A. chrysogenum strain was investigated by using response surface methodology (RSM). The Plackett-Burman design which involves two concentrations of each nutrient was effective in searching for the major medium components promoting CPC production. Under our experimental conditions; Soya oil, beet molasses and corn steep liquor were found to be the major factors contributing to the antibiotic production. Subsequently, a Box-Behnken design was used for outlining the concentration of the most effective medium constituents. Estimated optimum composition for the production of CPC was as follows: soya oil, 40 g/l; beet molasses, 180 g/l; and corn steep liquor, 330 g/l. The central composite design was used for outlining the optimum values of the fermentation parameters. Estimated optimum values for the production of CPC are as follows: inoculum level, 10(5.5) spores/ml; initial pH, 4.3; and aeration rate, 9364 ml/min. (C) 2006 Elsevier Ltd. All rights reserved.