Three species of Aspergillus (A. niger, A. flavus, A. nidulans) and two species of Acremonium (A. furcatum and A. kiliense) were tested for their potential to biosynthesis of cephalosporin-C (CPC) in batch mode of cultivation before and after mutagenesis. The effects of different ingredients of the medium on CPC yield were thoroughly investigated. Results manifested that sucrose 30 mg ml-1, DL methionine 3mg mL-1 and ammonium sulphate 7.5 mg mL-1 were most appropriate for maximum harvest of antibiotic. Mutants were achieved by exposing fungal cultures to 400 µg mL-1 of ethyl methane sulphonate (EMS) for 1 hour.