Production of cephalosporin C employing Acremonium chrysogenum ATCC 48272 under solid state fermentation was optimized. Different substrates like wheat bran, wheat rawa, bombay rawa, barley and rice bran were studied to optimize the best substrate. Wheat rawa showed the highest antibiotic yield. Physical and chemical parameters were optimized. The maximum productivity of cephalosporin C (22281 mug/g) was achieved by employing wheat rawa and with optimized process parameters including 1% w/w soluble starch and 1% w/w yeast extract as additives, incubation period of 5 days, incubation temperature at 30 degreesC, 1.5:10 (v/w) ratio of salt solution to weight of wheat bran, inoculum level 10% v/w, moisture content of solid substrate 80% and pH 6.5. (C) 2003 Published by Elsevier Science Ltd.